Have to temporarily disable Random-Things when generating a new Garden of Glass world, then re-enable when the world is created, not sure if this is a Garden of Glass issue or Random-Things issue, but it's easily repeatable.

Using the new 1.8.9 Botania.r1.8-248-MC1.8-0.6.1 / GardenOfGlass and RandomThings-MC1.8.9-3.6.2

It would appear it's something to do with it placing Nature Cores?

---- Minecraft Crash Report ----

WARNING: coremods are present:
NowWithRendering (hopperducts-mc1.8.8-1.4.6.jar)
LoadingPlugin (RandomThings-MC1.8.9-3.6.2.jar)
ThaumcraftLoader (Thaumcraft-1.8.9-5.1.6.jar)
FldLoadingPlugin (FastLeafDecay-1.8-1.6.jar)
FMLPlugin (InventoryTweaks-1.60-beta-31.jar)
thaumicinfusion (ThaumicInfusion-1.8.9-4.8.jar)
dsurroundcore (DynamicSurroundings-1.8.9-2.0.4.10.jar)
LoadingPlugin (ResourceLoader-MC1.8.8-1.4.jar)
Contact their authors BEFORE contacting forge

// Sorry :(

Time: 2/21/16 2:11 AM
Description: Exception initializing level

java.lang.NullPointerException: Exception initializing level
at lumien.randomthings.worldgen.WorldGenCores.placeNatureCore(WorldGenCores.java:262)
at lumien.randomthings.worldgen.WorldGenCores.generate(WorldGenCores.java:218)
at net.minecraftforge.fml.common.registry.GameRegistry.generateWorld(GameRegistry.java:112)
at net.minecraft.world.gen.ChunkProviderServer.func_73153_a(ChunkProviderServer.java:262)
at net.minecraft.world.chunk.Chunk.func_76624_a(Chunk.java:1053)
at net.minecraft.world.gen.ChunkProviderServer.originalLoadChunk(ChunkProviderServer.java:172)
at net.minecraft.world.gen.ChunkProviderServer.loadChunk(ChunkProviderServer.java:114)
at net.minecraft.world.gen.ChunkProviderServer.func_73158_c(ChunkProviderServer.java:84)
at net.minecraft.world.gen.ChunkProviderServer.func_73154_d(ChunkProviderServer.java:181)
at net.minecraft.world.World.func_72964_e(World.java:287)
at net.minecraft.world.World.func_175726_f(World.java:282)
at net.minecraft.world.World.func_180495_p(World.java:822)
at thaumcraft.common.lib.utils.BlockUtils.isBlockTouching(BlockUtils.java:361)
at thaumcraft.common.lib.world.ThaumcraftWorldGenerator.generateOres(ThaumcraftWorldGenerator.java:288)
at thaumcraft.common.lib.world.ThaumcraftWorldGenerator.generateAll(ThaumcraftWorldGenerator.java:312)
at thaumcraft.common.lib.world.ThaumcraftWorldGenerator.worldGeneration(ThaumcraftWorldGenerator.java:65)
at thaumcraft.common.lib.world.ThaumcraftWorldGenerator.generate(ThaumcraftWorldGenerator.java:53)
at net.minecraftforge.fml.common.registry.GameRegistry.generateWorld(GameRegistry.java:112)
at net.minecraft.world.gen.ChunkProviderServer.func_73153_a(ChunkProviderServer.java:262)
at net.minecraft.world.chunk.Chunk.func_76624_a(Chunk.java:1039)
at net.minecraft.world.gen.ChunkProviderServer.originalLoadChunk(ChunkProviderServer.java:172)
at net.minecraft.world.gen.ChunkProviderServer.loadChunk(ChunkProviderServer.java:114)
at net.minecraft.world.gen.ChunkProviderServer.func_73158_c(ChunkProviderServer.java:84)
at net.minecraft.world.gen.ChunkProviderServer.func_73154_d(ChunkProviderServer.java:181)
at net.minecraft.world.World.func_72964_e(World.java:287)
at net.minecraft.world.World.func_175726_f(World.java:282)
at net.minecraft.world.World.func_180495_p(World.java:822)
at thaumcraft.common.lib.utils.BlockUtils.isBlockTouching(BlockUtils.java:361)
at thaumcraft.common.lib.world.ThaumcraftWorldGenerator.generateOres(ThaumcraftWorldGenerator.java:288)
at thaumcraft.common.lib.world.ThaumcraftWorldGenerator.generateAll(ThaumcraftWorldGenerator.java:312)
at thaumcraft.common.lib.world.ThaumcraftWorldGenerator.worldGeneration(ThaumcraftWorldGenerator.java:65)
at thaumcraft.common.lib.world.ThaumcraftWorldGenerator.generate(ThaumcraftWorldGenerator.java:53)
at net.minecraftforge.fml.common.registry.GameRegistry.generateWorld(GameRegistry.java:112)
at net.minecraft.world.gen.ChunkProviderServer.func_73153_a(ChunkProviderServer.java:262)
at net.minecraft.world.chunk.Chunk.func_76624_a(Chunk.java:1081)
at net.minecraft.world.gen.ChunkProviderServer.originalLoadChunk(ChunkProviderServer.java:172)
at net.minecraft.world.gen.ChunkProviderServer.loadChunk(ChunkProviderServer.java:114)
at net.minecraft.world.gen.ChunkProviderServer.func_73158_c(ChunkProviderServer.java:84)
at net.minecraft.world.gen.ChunkProviderServer.func_73154_d(ChunkProviderServer.java:181)
at net.minecraft.world.World.func_72964_e(World.java:287)
at net.minecraft.world.World.func_175726_f(World.java:282)
at net.minecraft.world.World.func_180495_p(World.java:822)
at net.minecraft.world.World.func_175623_d(World.java:204)
at net.minecraft.world.World.func_175703_c(World.java:189)
at net.minecraft.world.WorldProvider.func_76566_a(WorldProvider.java:64)
at net.minecraft.world.WorldServer.func_73052_b(WorldServer.java:844)
at net.minecraft.world.WorldServer.func_72963_a(WorldServer.java:766)
at net.minecraft.server.integrated.IntegratedServer.func_71247_a(IntegratedServer.java:89)
at net.minecraft.server.integrated.IntegratedServer.func_71197_b(IntegratedServer.java:123)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:441)
at java.lang.Thread.run(Unknown Source)

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

-- Head --
Stacktrace:
at lumien.randomthings.worldgen.WorldGenCores.placeNatureCore(WorldGenCores.java:262)
at lumien.randomthings.worldgen.WorldGenCores.generate(WorldGenCores.java:218)
at net.minecraftforge.fml.common.registry.GameRegistry.generateWorld(GameRegistry.java:112)
at net.minecraft.world.gen.ChunkProviderServer.func_73153_a(ChunkProviderServer.java:262)
at net.minecraft.world.chunk.Chunk.func_76624_a(Chunk.java:1053)
at net.minecraft.world.gen.ChunkProviderServer.originalLoadChunk(ChunkProviderServer.java:172)
at net.minecraft.world.gen.ChunkProviderServer.loadChunk(ChunkProviderServer.java:114)
at net.minecraft.world.gen.ChunkProviderServer.func_73158_c(ChunkProviderServer.java:84)
at net.minecraft.world.gen.ChunkProviderServer.func_73154_d(ChunkProviderServer.java:181)
at net.minecraft.world.World.func_72964_e(World.java:287)
at net.minecraft.world.World.func_175726_f(World.java:282)
at net.minecraft.world.World.func_180495_p(World.java:822)
at thaumcraft.common.lib.utils.BlockUtils.isBlockTouching(BlockUtils.java:361)
at thaumcraft.common.lib.world.ThaumcraftWorldGenerator.generateOres(ThaumcraftWorldGenerator.java:288)
at thaumcraft.common.lib.world.ThaumcraftWorldGenerator.generateAll(ThaumcraftWorldGenerator.java:312)
at thaumcraft.common.lib.world.ThaumcraftWorldGenerator.worldGeneration(ThaumcraftWorldGenerator.java:65)
at thaumcraft.common.lib.world.ThaumcraftWorldGenerator.generate(ThaumcraftWorldGenerator.java:53)
at net.minecraftforge.fml.common.registry.GameRegistry.generateWorld(GameRegistry.java:112)
at net.minecraft.world.gen.ChunkProviderServer.func_73153_a(ChunkProviderServer.java:262)
at net.minecraft.world.chunk.Chunk.func_76624_a(Chunk.java:1039)
at net.minecraft.world.gen.ChunkProviderServer.originalLoadChunk(ChunkProviderServer.java:172)
at net.minecraft.world.gen.ChunkProviderServer.loadChunk(ChunkProviderServer.java:114)
at net.minecraft.world.gen.ChunkProviderServer.func_73158_c(ChunkProviderServer.java:84)
at net.minecraft.world.gen.ChunkProviderServer.func_73154_d(ChunkProviderServer.java:181)
at net.minecraft.world.World.func_72964_e(World.java:287)
at net.minecraft.world.World.func_175726_f(World.java:282)
at net.minecraft.world.World.func_180495_p(World.java:822)
at thaumcraft.common.lib.utils.BlockUtils.isBlockTouching(BlockUtils.java:361)
at thaumcraft.common.lib.world.ThaumcraftWorldGenerator.generateOres(ThaumcraftWorldGenerator.java:288)
at thaumcraft.common.lib.world.ThaumcraftWorldGenerator.generateAll(ThaumcraftWorldGenerator.java:312)
at thaumcraft.common.lib.world.ThaumcraftWorldGenerator.worldGeneration(ThaumcraftWorldGenerator.java:65)
at thaumcraft.common.lib.world.ThaumcraftWorldGenerator.generate(ThaumcraftWorldGenerator.java:53)
at net.minecraftforge.fml.common.registry.GameRegistry.generateWorld(GameRegistry.java:112)
at net.minecraft.world.gen.ChunkProviderServer.func_73153_a(ChunkProviderServer.java:262)
at net.minecraft.world.chunk.Chunk.func_76624_a(Chunk.java:1081)
at net.minecraft.world.gen.ChunkProviderServer.originalLoadChunk(ChunkProviderServer.java:172)
at net.minecraft.world.gen.ChunkProviderServer.loadChunk(ChunkProviderServer.java:114)
at net.minecraft.world.gen.ChunkProviderServer.func_73158_c(ChunkProviderServer.java:84)
at net.minecraft.world.gen.ChunkProviderServer.func_73154_d(ChunkProviderServer.java:181)
at net.minecraft.world.World.func_72964_e(World.java:287)
at net.minecraft.world.World.func_175726_f(World.java:282)
at net.minecraft.world.World.func_180495_p(World.java:822)
at net.minecraft.world.World.func_175623_d(World.java:204)
at net.minecraft.world.World.func_175703_c(World.java:189)
at net.minecraft.world.WorldProvider.func_76566_a(WorldProvider.java:64)
at net.minecraft.world.WorldServer.func_73052_b(WorldServer.java:844)

-- Affected level --
Details:
Level name: MyGlassWorld
All players: 0 total; []
Chunk stats: ServerChunkCache: 1006 Drop: 0
Level seed: 1629188324667095803
Level generator: ID 07 - botania-skyblock, ver 0. Features enabled: true
Level generator options:
Level spawn location: 0.00,0.00,0.00 - World: (0,0,0), Chunk: (at 0,0,0 in 0,0; contains blocks 0,0,0 to 15,255,15), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Level time: 0 game time, 0 day time
Level dimension: 0
Level storage version: 0x04ABD - Anvil
Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: true
Stacktrace:
at net.minecraft.world.WorldServer.func_72963_a(WorldServer.java:766)
at net.minecraft.server.integrated.IntegratedServer.func_71247_a(IntegratedServer.java:89)
at net.minecraft.server.integrated.IntegratedServer.func_71197_b(IntegratedServer.java:123)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:441)
at java.lang.Thread.run(Unknown Source)

-- System Details --
Details:
Minecraft Version: 1.8.9
Operating System: Windows 10 (amd64) version 10.0
Java Version: 1.8.0_73, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 2072873784 bytes (1976 MB) / 3325034496 bytes (3171 MB) up to 5726797824 bytes (5461 MB)
JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx6G
IntCache: cache: 0, tcache: 0, allocated: 15, tallocated: 95
FML: MCP 9.19 Powered by Forge 11.15.1.1756 84 mods loaded, 84 mods active
States: 'U' = Unloaded 'L' = Loaded 'C' = Constructed 'H' = Pre-initialized 'I' = Initialized 'J' = Post-initialized 'A' = Available 'D' = Disabled 'E' = Errored
UCHIJAA mcp{9.19} Minecraft Coder Pack
UCHIJAA FML{8.0.99.99} Forge Mod Loader
UCHIJAA Forge{11.15.1.1756} Minecraft Forge
UCHIJAA Baubles{1.1.3.0} Baubles
UCHIJAA aura{591} Aura Cascade
UCHIJAA bagginses{2.1.5b} Bagginses
UCHIJAA BetterAchievements{0.1.1} Better Achievements
UCHIJAA BetterThanBunnies{1.8.9-1.0.1} BetterThanBunnies
UCHIJAA BiomesOPlenty{3.0.0} Biomes O' Plenty
UCHIJAA Waila{1.6.0} Waila
UCHIJAA intangible{0.0.23} Intangible
UCHIJAA JEI{2.28.1.161} Just Enough Items
UCHIJAA BloodMagic{1.8.9-2.0.0-18} Blood Magic: Alchemical Wizardry
UCHIJAA bookshelfapi{2.3.2} Bookshelf
UCHIJAA Thaumcraft{5.1.6} Thaumcraft
UCHIJAA Botania{r1.8-249} Botania
UCHIJAA BuildCraft|Core{7.2.0-pre11} BuildCraft
UCHIJAA BuildCraft|Transport{7.2.0-pre11} BC Transport
UCHIJAA BuildCraft|Factory{7.2.0-pre11} BC Factory
UCHIJAA BuildCraft|Silicon{7.2.0-pre11} BC Silicon
UCHIJAA BuildCraft|Robotics{7.2.0-pre11} BC Robotics
UCHIJAA BuildCraft|Energy{7.2.0-pre11} BC Energy
UCHIJAA BuildCraft|Builders{7.2.0-pre11} BC Builders
UCHIJAA buildingbrickscompatvanilla{1.8.9-1.3.2} Building Bricks Vanilla Compat
UCHIJAA buildingbricks{1.8.9-1.3.2} Building Bricks
UCHIJAA Chameleon{1.8.9-0.2.1} Chameleon
UCHIJAA mcmultipart{1.0.7} MCMultiPart
UCHIJAA CharsetLib{0.2.1} ‽
UCHIJAA CharsetTweaks{0.2.1} *
UCHIJAA CharsetWires{0.2.1} +
UCHIJAA CharsetAudio{0.2.1} ♫
UCHIJAA CharsetStorage{0.2.1} #
UCHIJAA CharsetPipes{0.2.1} |
UCHIJAA CharsetGates{0.2.1} &
UCHIJAA chisel{@Version@} Chisel
UCHIJAA chiselsandbits{mc1.8.9-v1.8.10} Chisels & Bits
UCHIJAA compasscoords{1.8.9-0.2.6} Compass Co-ords
UCHIJAA ComputerCraft{1.78} ComputerCraft
UCHIJAA craftingtweaks{3.0.41} Crafting Tweaks
UCHIJAA crafttweaker{3.0.0} crafttweaker
UCHIJAA CustomMainMenu{2.0} Custom Main Menu
UCHIJAA dsurround{2.0.4.10} Dynamic Surroundings
UCHIJAA ShetiPhianCore{3.1.0} ShetiPhian-Core
UCHIJAA EnderTanks{1.2.1} EnderTanks
UCHIJAA exnihilo2{0.28} Ex Nihilo 2
UCHIJAA ezstorage{1.0} EZ Storage
UCHIJAA fastleafdecay{1.6} Fast Leaf Decay
UCHIJAA flatcoloredblocks{mc1.8.9-v1.3} Flat Colored Blocks
UCHIJAA FTBL{2.0.2} FTBLib
UCHIJAA FTBU{2.0.2} FTBUtilities
UCHIJAA furnus{1.7} Furnus
UCHIJAA GardenOfGlass{sqrt(-1)} Garden of Glass
UCHIJAA graves{1.8.9-b39-universal} Graves Mod
UCHIJAA hopperducts{1.4.6} Hopper Ducts
UCHIJAA k4lib{1.8.9-1.0.16} K4Lib
UCHIJAA HydCraft{1.8.9-3.1.65} Hydraulicraft
UCHIJAA IGWMod{1.2.3-3} In-Game wiki Mod
UCHIJAA inventorysorter{0.7.4+26} Simple Inventory sorting
UCHIJAA inventorytweaks{1.60-beta-31-0aadb96} Inventory Tweaks
UCHIJAA IronChest{6.0.125.770} Iron Chest
UCHIJAA JEIAddons{0.12.0.57} Just Enough Items Addons
UCHIJAA journeymap{5.1.3} JourneyMap
UCHIJAA jeresources{0.3.4} Just Enough Resources
UCHIJAA llor{1.0.4-mc1.8.8} Light Level Overlay Reloaded
UCHIJAA mantle{1.8.9-0.7.jenkins72} Mantle
UCHIJAA testdummy{1.0} MmmMmmMmmMmm
UCHIJAA MoreFurnaces{1.5.0} More Furnaces
UCHIJAA Morpheus{1.8.9-2.0.58} Morpheus
UCHIJAA MouseTweaks{2.6.0} Mouse Tweaks
UCHIJAA neotech{2.3.7} NeoTech
UCHIJAA fodc{1.7.2} Ore Dictionary Converter
UCHIJAA playerrugs{0.0.1} Player Rugs
UCHIJAA PneumaticCraft{1.13.6} PneumaticCraft
UCHIJAA progressiveautomation{1.6.35} Progressive Automation
UCHIJAA Psi{beta-14} Psi
UCHIJAA RandomThings{3.6.2} Random Things
UCHIJAA ResourceLoader{1.4} Resource Loader
UCHIJAA rftools{4.22beta22} RFTools
UCHIJAA Roguelike{1.4.5} Roguelike Dungeons
UCHIJAA simpleretrogen{2.2.2+3} Simple Retrogen
UCHIJAA StorageDrawers{1.8.9-2.4.1} Storage Drawers
UCHIJAA tconstruct{1.8.9-2.0.2.jenkins61} Tinkers' Construct
UCHIJAA thaumicinfusion{4.8} Thaumic Infusion
UCHIJAA wawla{1.4.7} What Are We Looking At
Loaded coremods (and transformers):
NowWithRendering (hopperducts-mc1.8.8-1.4.6.jar)
net.fybertech.nwr.NowWithRendering
LoadingPlugin (RandomThings-MC1.8.9-3.6.2.jar)
lumien.randomthings.asm.ClassTransformer
ThaumcraftLoader (Thaumcraft-1.8.9-5.1.6.jar)

FldLoadingPlugin (FastLeafDecay-1.8-1.6.jar)
com.olafski.fastleafdecay.FldTransformer
FMLPlugin (InventoryTweaks-1.60-beta-31.jar)
invtweaks.forge.asm.ContainerTransformer
thaumicinfusion (ThaumicInfusion-1.8.9-4.8.jar)
drunkmafia.thaumicinfusion.common.asm.BlockTransformer
drunkmafia.thaumicinfusion.common.asm.WorldTransformer
dsurroundcore (DynamicSurroundings-1.8.9-2.0.4.10.jar)
org.blockartistry.mod.DynSurround.asm.Transformer
LoadingPlugin (ResourceLoader-MC1.8.8-1.4.jar)
lumien.resourceloader.asm.ClassTransformer
GL info: ERROR RuntimeException: No OpenGL context found in the current thread.
Pulsar/tconstruct loaded Pulses:
- TinkerCommons (Enabled/Forced)
- TinkerWorld (Enabled/Not Forced)
- TinkerTools (Enabled/Not Forced)
- TinkerSmeltery (Enabled/Not Forced)
- TinkerGadgets (Enabled/Not Forced)
- TinkerOredict (Enabled/Forced)
- TinkerIntegration (Enabled/Forced)
- TinkerFluids (Enabled/Forced)
- TinkerMaterials (Enabled/Forced)
- chiselsandbitsIntegration (Enabled/Not Forced)
- craftingtweaksIntegration (Enabled/Not Forced)
- TinkerDebug (Enabled/Not Forced)

Profiler Position: N/A (disabled)
Player Count: 0 / 8; []
Type: Integrated Server (map_client.txt)
Is Modded: Definitely; Client brand changed to 'fml,forge'

Is there a log?