We entered the nether via portal and server crash. See crash report below..

---- Minecraft Crash Report ----
// This is a token for 1 free hug. Redeem at your nearest Mojangsta: [HUG]

Time: 9/14/20, 11:12 PM
Description: Exception generating new chunk

java.lang.IllegalArgumentException: bound must be positive
at java.base/java.util.Random.nextInt(Random.java:388)
at net.minecraft.class_3785.method_16631(class_3785.java:131)
at net.minecraft.class_3778.method_30419(class_3778.java:266)
at com.telepathicgrunt.repurposedstructures.world.structures.pieces.GeneralJigsawGenerator.addPieces(GeneralJigsawGenerator.java:23)
at com.telepathicgrunt.repurposedstructures.world.structures.TempleNetherStructure$Start.init(TempleNetherStructure.java:37)
at com.telepathicgrunt.repurposedstructures.world.structures.TempleNetherStructure$Start.method_16655(TempleNetherStructure.java:30)
at net.minecraft.class_3195.method_28657(class_3195.java:261)
at net.minecraft.class_5312.method_28622(class_5312.java:35)
at net.minecraft.class_2794.method_28508(class_2794.java:278)
at net.minecraft.class_2794.method_16129(class_2794.java:267)
at net.minecraft.class_2806.method_16556(class_2806.java:51)
at net.minecraft.class_2806.method_12154(class_2806.java:219)
at net.minecraft.class_3898.method_17225(class_3898.java:568)
at com.mojang.datafixers.util.Either$Left.map(Either.java:38)
at net.minecraft.class_3898.method_17224(class_3898.java:562)
at java.base/java.util.concurrent.CompletableFuture$UniCompose.tryFire(CompletableFuture.java:1072)
at java.base/java.util.concurrent.CompletableFuture$Completion.run(CompletableFuture.java:478)
at net.minecraft.class_3900.method_17634(class_3900.java:58)
at net.minecraft.class_3846.method_16907(class_3846.java:94)
at net.minecraft.class_3846.method_16900(class_3846.java:137)
at net.minecraft.class_3846.run(class_3846.java:105)
at java.base/java.util.concurrent.ForkJoinTask$RunnableExecuteAction.exec(ForkJoinTask.java:1426)
at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:290)
at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1020)
at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1656)
at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1594)
at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:183)

A detailed walkthrough of the error, its code path and all known details is as follows:

-- Head --
Thread: Server thread
Stacktrace:
at java.base/java.util.Random.nextInt(Random.java:388)
at net.minecraft.class_3785.method_16631(class_3785.java:131)
at net.minecraft.class_3778.method_30419(class_3778.java:266)
at com.telepathicgrunt.repurposedstructures.world.structures.pieces.GeneralJigsawGenerator.addPieces(GeneralJigsawGenerator.java:23)
at com.telepathicgrunt.repurposedstructures.world.structures.TempleNetherStructure$Start.init(TempleNetherStructure.java:37)
at com.telepathicgrunt.repurposedstructures.world.structures.TempleNetherStructure$Start.method_16655(TempleNetherStructure.java:30)
at net.minecraft.class_3195.method_28657(class_3195.java:261)
at net.minecraft.class_5312.method_28622(class_5312.java:35)
at net.minecraft.class_2794.method_28508(class_2794.java:278)
at net.minecraft.class_2794.method_16129(class_2794.java:267)
at net.minecraft.class_2806.method_16556(class_2806.java:51)
at net.minecraft.class_2806.method_12154(class_2806.java:219)

-- Chunk to be generated --
Details:
Location: 2,-21
Position hash: -90194313214
Generator: net.minecraft.class_3754@67852777
Stacktrace:
at net.minecraft.class_3898.method_17225(class_3898.java:568)
at com.mojang.datafixers.util.Either$Left.map(Either.java:38)
at net.minecraft.class_3898.method_17224(class_3898.java:562)
at java.base/java.util.concurrent.CompletableFuture$UniCompose.tryFire(CompletableFuture.java:1072)
at java.base/java.util.concurrent.CompletableFuture$Completion.run(CompletableFuture.java:478)
at net.minecraft.class_3900.method_17634(class_3900.java:58)
at net.minecraft.class_3846.method_16907(class_3846.java:94)
at net.minecraft.class_3846.method_16900(class_3846.java:137)
at net.minecraft.class_3846.run(class_3846.java:105)

-- Affected level --
Details:
All players: 1 total; [class_3222['CableRunner'/180, l='ServerLevel[world]', x=-13.96, y=69.00, z=-6.79]]
Chunk stats: ServerChunkCache: 1833
Level dimension: minecraft:the_nether
Derived: true
Level spawn location: World: (-134,65,-71), Chunk: (at 10,4,9 in -9,-5; contains blocks -144,0,-80 to -129,255,-65), Region: (-1,-1; contains chunks -32,-32 to -1,-1, blocks -512,0,-512 to -1,255,-1)
Level time: 1783896 game time, 213954 day time
Level name: world
Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: false
Level weather: Rain time: 72355 (now: false), thunder time: 133276 (now: false)
Known server brands: fabric
Level was modded: true
Level storage version: 0x04ABD - Anvil
Stacktrace:
at net.minecraft.server.MinecraftServer.method_3813(MinecraftServer.java:871)
at net.minecraft.class_3176.method_3813(class_3176.java:303)
at net.minecraft.server.MinecraftServer.method_3748(MinecraftServer.java:808)
at net.minecraft.server.MinecraftServer.method_29741(MinecraftServer.java:667)
at net.minecraft.server.MinecraftServer.method_29739(MinecraftServer.java:254)
at java.base/java.lang.Thread.run(Thread.java:834)

-- System Details --
Details:
Minecraft Version: 1.16.2
Minecraft Version ID: 1.16.2
Operating System: Linux (amd64) version 4.19.0-10-cloud-amd64
Java Version: 11.0.8, Debian
Java VM Version: OpenJDK 64-Bit Server VM (mixed mode, sharing), Debian
Memory: 3586046952 bytes (3419 MB) / 4874829824 bytes (4649 MB) up to 7516192768 bytes (7168 MB)
CPUs: 4
JVM Flags: 1 total; -Xmx7168M
Fabric Mods:
adorn: Adorn 1.11.0+1.16.2
adventurez: AdventureZ 1.0.10
allure: Allure 1.2.6
angerable-patch: Angerable Patch 1.0.0-1.16.1
appleskin: AppleSkin 1.0.11
appliedenergistics2: Applied Energistics 2 8.1.0-alpha.9
artifice: Artifice 0.13.1+1.16.2-rc1
astromine: Astromine 1.10.4+fabric-1.16.2
astromine-core: Astromine: Core 1.10.4+fabric-1.16.2
astromine-discoveries: Astromine: Discoveries 1.10.4+fabric-1.16.2
astromine-foundations: Astromine: Foundations 1.10.4+fabric-1.16.2
astromine-technologies: Astromine: Technologies 1.10.4+fabric-1.16.2
astromine-transportations: Astromine: Transportations 1.10.4+fabric-1.16.2
autoconfig1u: Auto Config v1 Updated 3.2.2
bambootweaks: Bamboo Tweaks unspecified
bedspreads: Bedspreads 1.1.0-1.16.2
blade: Blade 1.0.1
blockus: Blockus 1.6.3.2
blue_endless_jankson: jankson +
byg: BYG 1.0.7
campanion: Campanion 1.2.0+build.39
cardinal-components: Cardinal Components API 2.6.0
cardinal-components-base: Cardinal Components API (base) 2.6.0
cardinal-components-block: Cardinal Components API (blocks) 2.6.0
cardinal-components-chunk: Cardinal Components API (chunks) 2.6.0
cardinal-components-entity: Cardinal Components API (entities) 2.6.0
cardinal-components-item: Cardinal Components API (items) 2.6.0
cardinal-components-level: Cardinal Components API (world saves) 2.6.0
cardinal-components-scoreboard: Cardinal Components API (scoreboard) 2.6.0
cardinal-components-util: Cardinal Components API (utilities) 2.6.0
cardinal-components-world: Cardinal Components API (worlds) 2.6.0
cavebiomes: Cave Biomes 0.3.0
ce_foodstuffs: Common Expansion: Foodstuffs 1.0.1
chainmail: Chainmail 0.5.0
chunkpregen: Fabric Chunk Pregenerator 0.3.0
cleancut: CleanCut mc1.16-2.1-fabric
cloth-api: Cloth API 1.4.8
cloth-armor-api-v1: Cloth Armor API v1 1.4.8
cloth-basic-math: Cloth Basic Math 0.5.1
cloth-client-events-v0: Cloth Client Events v0 1.4.8
cloth-common-events-v1: Cloth Common Events v1 1.4.8
cloth-config2: Cloth Config v4 4.8.1
cloth-datagen-api-v1: Cloth Datagen v1 1.4.8
cloth-durability-bar-api-v1: Cloth Durability Bar API v1 1.4.8
cloth-dynamic-registry-api-v1: Cloth Dynamic Registry API v1 1.4.8
cloth-utils-v1: Cloth Utils v1 1.4.8
com_electronwill_night-config_core: core 3.6.0
com_electronwill_night-config_toml: toml 3.6.0
com_github_therandomlabs_trlutils-config: TRLUtils-Config master-SNAPSHOT
com_github_therandomlabs_trlutils-fabric: TRLUtils-Fabric 1.16-SNAPSHOT
com_moandjiezana_toml_toml4j: toml4j 0.7.2
compressedblocks: Compressed Blocks 1.0
computercraft: CC:T for Fabric 1.91.1
controlling: Controlling For Fabric 1.1.2
cotton: Cotton 1.0.7
cotton-cauldron: Cotton Cauldron 1.0.4
cotton-commons: Cotton Commons 1.0.4
cotton-config: Cotton Config 1.0.0-rc.7
cotton-datapack: Cotton Datapack 1.0.7
cotton-logging: Cotton Logging 1.0.0-rc.4
cotton-player-events: Cotton Player Events 1.0.2
couplings: Couplings 1.3.1
crookedcrooks: Crooked Crooks 1.3.0+1.16.3
crusade: Crusade 1.1.4+1.16.2
dankstorage: Dank Storage 1.7-1.16.2
diggusmaximus: Diggus Maximus 1.3.1-1.16
dml-refabricated: Deep Mob Learning: Refabricated 0.3.1-beta1
dwarfcoal: Dwarf Coal 1.16.2-1.0.0
eggtab: Egg Tab 1.3.0+1.16-fabric
endreborn: End: Rebellion 1.8
expandedstorage: ExpandedStorage 5.6.26
ezpas: Ezpas 1.2.2-1.16.2
fabric: Fabric API 0.20.1+build.401-1.16
fabric-api-base: Fabric API Base 0.1.3+12a8474cfa
fabric-command-api-v1: Fabric Command API (v1) 1.0.8+5ce533984e
fabric-commands-v0: Fabric Commands (v0) 0.2.0+52d308364e
fabric-containers-v0: Fabric Containers (v0) 0.1.8+045df74f4e
fabric-content-registries-v0: Fabric Content Registries (v0) 0.1.9+059ea8664e
fabric-crash-report-info-v1: Fabric Crash Report Info (v1) 0.1.2+b7f9825d4e
fabric-diagonal-panes: Fabric Diagonal Panes 0.3.1
fabric-events-interaction-v0: Fabric Events Interaction (v0) 0.4.0+e2e6cdad4e
fabric-events-lifecycle-v0: Fabric Events Lifecycle (v0) 0.2.0+16acbe5b4e
fabric-furnaces: Fabric Furnaces 1.3.2-1.16.2
fabric-game-rule-api-v1: Fabric Game Rule API (v1) 1.0.1+91555cd14e
fabric-item-api-v1: Fabric Item API (v1) 1.1.0+29679fd64e
fabric-item-groups-v0: Fabric Item Groups (v0) 0.2.0+438f96364e
fabric-language-kotlin: Fabric Language Kotlin 1.4.0+build.1
fabric-lifecycle-events-v1: Fabric Lifecycle Events (v1) 1.2.0+74cc3b204e
fabric-loot-tables-v1: Fabric Loot Tables (v1) 1.0.1+432ea1884e
fabric-mining-levels-v0: Fabric Mining Levels (v0) 0.1.2+b764ce994e
fabric-networking-blockentity-v0: Fabric Networking Block Entity (v0) 0.2.5+b50ffc7b4e
fabric-networking-v0: Fabric Networking (v0) 0.1.10+e00ecb5f4e
fabric-object-builder-api-v1: Fabric Object Builder API (v1) 1.7.0+432ea1884e
fabric-object-builders-v0: Fabric Object Builders (v0) 0.7.0+432ea1884e
fabric-particles-v1: fabric-particles-v1 0.2.2+fb0d9b0e4e
fabric-registry-sync-v0: Fabric Registry Sync (v0) 0.4.5+fcdfdfa14e
fabric-rendering-data-attachment-v1: Fabric Rendering Data Attachment (v1) 0.1.3+b7f9825d4e
fabric-resource-loader-v0: Fabric Resource Loader (v0) 0.3.1+facf3bbf4e
fabric-screen-handler-api-v1: Fabric Screen Handler API (v1) 1.1.0+872498414e
fabric-structure-api-v1: Fabric Structure API (v1) 1.0.1+fb0d9b0e4e
fabric-tag-extensions-v0: Fabric Tag Extensions (v0) 1.0.3+ac8e8c594e
fabric-tool-attribute-api-v1: Fabric Tool Attribute API (v1) 1.2.2+ccce563e4e
fabricloader: Fabric Loader 0.9.2+build.206
fallflyinglib: FallFlyingLib 1.1.0
fatxporbs: Fat Experience Orbs 0.0.7
fermion: Fermion 2.1.191
fermion-modkeys: Fermion Modifier Keys 1.8.180-snapshot
fiber: fiber 0.23.0-2
flonters: Flonters 1.1.1+1.16.2
flora-doubling: Flora Doubling 1.1.2
gameinfo: GameInfo 2.0.0a-experimental-06.1 1.16.2
givemehats: Give Me Hats! 1.2.8
glassdoor: Glass Doors 1.4.4-1.16
glassential: Glassential 1.16.1-1.1.4
goml: Get Off My Lawn 1.1.0
hard-hat-steve: Hard Hat Steve 1.1.1
hardcorequesting: Hardcore Questing Mode 0.3.1
harvest: Harvest 1.2.12
hctm-base: HCTM Base 3.4.0
horseinfo: Horse Info 0.2.2-1.16.1
improved-stations: Improved Stations 2.0.3
indrev: Industrial Revolution 1.6.6-BETA
inmis: Inmis 1.3.0-1.16.2
inventorysorter: Inventory Sorter 1.7.2-1.16
iron-jetpacks: Iron Jetpacks 0.2.5
jankson: Jankson 3.0.1+j1.2.0
javax_vecmath_vecmath: vecmath 1.5.2
jumploader: Jumploader 2.0.1
kibe: Kibe 1.4.2-BETA
ktdatataglib: KtDataTagLib 1.4.0
kubejs: KubeJS 1.4.5
kyrptconfig: Kytpt Config 1.1.2-1.16
lapisreserve: Lapis Reserve 1.0.6
libblockattributes_core: LibBlockAttributes (Core) 0.8.2-pre.6
libblockattributes_fluids: LibBlockAttributes (Fluids) 0.8.2-pre.6
libblockattributes_items: LibBlockAttributes (Items) 0.8.2-pre.6
libcd: LibCapableData 2.5.0+1.16.2
libgui: LibGui 3.0.0-beta.1+1.16.2-rc2
libstructure: LibStructure 1.5
linkart: Linkart unspecified
lithium: Lithium 0.5.4
magna: Magna 1.4.2-1.16.2
mambience: MAmbience 2.1.0+1.16.2
maybe-data: Maybe data 1.0.0-1.16.2
mcdict: MCDict 1.0.0+1.16.2
minecraft: Minecraft 1.16.2
mm: Manningham Mills 2.0
org_codehaus_groovy_groovy: groovy 3.0.3
org_codehaus_groovy_groovy-jsr223: groovy-jsr223 3.0.3
org_jetbrains_annotations: annotations 20.0.0
org_jetbrains_kotlin_kotlin-reflect: kotlin-reflect 1.4.0
org_jetbrains_kotlin_kotlin-stdlib: kotlin-stdlib 1.4.0
org_jetbrains_kotlin_kotlin-stdlib-jdk7: kotlin-stdlib-jdk7 1.4.0
org_jetbrains_kotlin_kotlin-stdlib-jdk8: kotlin-stdlib-jdk8 1.4.0
org_jetbrains_kotlinx_kotlinx-coroutines-jdk8: kotlinx-coroutines-jdk8 1.3.9
org_joml_joml: joml 1.9.25
packages: Packages 1.1
parchment: Parchment 1.0.2+1.15.2
patchouli: Patchouli 1.16-40-FABRIC
phosphor: Phosphor 0.6.0+build.7
playerabilitylib: Pal 1.2.1
qcommon-cfg-core: qcommon-cfg-core 3.2.0
qcommon-croco: Croco 2.1.1
quickshulker: Quick Shulker 1.1.6-1.16
reach-entity-attributes: Reach Entity Attribute 1.0.1
reborncore: Reborn Core 4.4.1+build.69
repurposed_structures: Repurposed Structures 1.16.2-1.5.4
respawnablepets: Respawnable Pets 6
rgbable: RGBable 1.0.0
ringsofascension: Rings of Ascension 1.0.7
roughlyenoughitems: Roughly Enough Items 5.4.2
roughlyenoughitems-api: REI (API) 5.4.2
roughlyenoughitems-default-plugin: REI (Default Plugin) 5.4.2
roughlyenoughitems-runtime: REI (Runtime) 5.4.2
roughlyenoughresources: Roughly Enough Resources 2.1.1
rswires: RSWires 4.9.1
rtree-3i-lite-fabric: rtree-3i-lite for Fabric 0.3.0
sandwichable: Sandwichable 1.1.2
secretrooms: Secret Rooms 0.9.2+1.16.2
shapes: Shapes 2.0.0+build.10
shulkerboxtooltip: Shulker Box Tootip 2.1.1+1.16.2
simpleteleporters: Simple Teleporters 2.2.1
slabhelper: Slab Helper 1.3.4
smootherbedrock: Smoother Bedrock 1.0.0
staffofbuilding: Staff of Building 1.2.2-1.16.2
static-content: Static Content 1.0.1-1.16.2
staticdata: Static Data 1.1.2
stonecutter-tweaks: Stonecutter Tweaks 1.1.0-1.16
structure-helpers: Structure Helpers 3.0.0
tacocraft: TacoCraft 1.3.1+mc.1.16
team_reborn_energy: Energy 0.1.0
techreborn: Tech Reborn 3.5.3+build.115
tis3d: TIS-3D 1.5.0
tk_valoeghese_zoesteriaconfig: ZoesteriaConfig 1.3.2
trapexpansion: Trap Expansion 1.3.2
trees-do-not-float: Trees Do Not Float 1.12.94
trinkets: Trinkets 2.6.4
universalcomponents: Universal Components 0.7.3+1.16.2
vanilla-hammers: Vanilla Hammers 2.0.8-1.16.2
vanilladeathchest: VanillaDeathChest 1.16.2-1.11.0.6-fabric
vanillaexcavators: Vanilla Excavators 1.1.0
villagerhats: Villager Hats fabric-1.16-rc1-1.0.0
waila: Hwyla 1.9.22
winged: Winged Mod 1.16.2-1.4.0
wolveswitharmor: Wolves With Armor 1.5.2-1.16.2
woodenhoppers: Wooden Hoppers 1.0.0
wrenchable: Wrenchable 1.0.0+1.16.1
xaerominimap: Xaero's Minimap 20.21.0
xaeroworldmap: Xaero's World Map 1.10.3
xpstorage: XP Storage 0.4.1+1.16.2
yosbr: YOSBR 0.1.1
Player Count: 1 / 10; [class_3222['CableRunner'/180, l='ServerLevel[world]', x=-13.96, y=69.00, z=-6.79]]
Data Packs: vanilla (incompatible), fabric/adorn, fabric/adventurez, fabric/allure, fabric/appliedenergistics2, fabric/astromine-core, fabric/astromine-discoveries, fabric/astromine-foundations, fabric/astromine-technologies, fabric/astromine-transportations, fabric/bambootweaks, fabric/bedspreads, fabric/blockus (incompatible), fabric/byg, fabric/campanion, fabric/ce_foodstuffs, fabric/compressedblocks, fabric/computercraft (incompatible), fabric/cotton-commons, fabric/crookedcrooks, fabric/crusade, fabric/dankstorage, fabric/dml-refabricated, fabric/dwarfcoal, fabric/endreborn, fabric/expandedstorage, fabric/ezpas, fabric/fabric-furnaces, fabric/fabric-tool-attribute-api-v1, fabric/flonters, fabric/flora-doubling (incompatible), fabric/glassdoor, fabric/glassential, fabric/goml, fabric/hard-hat-steve (incompatible), fabric/hardcorequesting, fabric/harvest, fabric/hctm-base, fabric/improved-stations, fabric/indrev, fabric/inmis, fabric/iron-jetpacks (incompatible), fabric/kibe, fabric/kubejs (incompatible), fabric/libcd, fabric/linkart, fabric/maybe-data, fabric/packages, fabric/repurposed_structures, fabric/respawnablepets, fabric/rswires, fabric/sandwichable, fabric/secretrooms, fabric/simpleteleporters, fabric/slabhelper, fabric/staffofbuilding, fabric/structure-helpers, fabric/tacocraft, fabric/techreborn, fabric/tis3d (incompatible), fabric/trapexpansion, fabric/vanilla-hammers, fabric/vanillaexcavators, fabric/villagerhats, fabric/winged, fabric/wolveswitharmor, fabric/woodenhoppers, fabric/xpstorage, global/cotton_generated (incompatible), secretrooms:server_pack
Is Modded: Definitely; Server brand changed to 'fabric'
Type: Dedicated Server (map_server.txt)

Have you made a datapack to go with the modpack? Was the modpack put on a server and you started playing on it right after the server created the world for the very first time?