So, i've been tinkering with this mod for a while, and while i was playing single-player normally, everything was working well and crash-less-ly... However, opening bags with a custom config somehow makes them crash.
---- Minecraft Crash Report ----
// Hi. I'm Minecraft, and I'm a crashaholic.

Time: 31/10/15 03:40
Description: Ticking memory connection

java.lang.IllegalArgumentException: bound must be positive
at java.util.Random.nextInt(Unknown Source)
at net.minecraftforge.common.ChestGenHooks.generateStacks(ChestGenHooks.java:111)
at mal.lootbags.LootMap.getRandomItem(LootMap.java:404)
at mal.lootbags.item.LootbagItem.getLootItem(LootbagItem.java:397)
at mal.lootbags.item.LootbagItem.getLootItem(LootbagItem.java:326)
at mal.lootbags.item.LootbagItem.generateInventory(LootbagItem.java:304)
at mal.lootbags.item.LootbagItem.func_77659_a(LootbagItem.java:524)
at net.minecraft.item.ItemStack.func_77957_a(ItemStack.java:146)
at net.minecraft.server.management.ItemInWorldManager.func_73085_a(ItemInWorldManager.java:316)
at net.minecraft.network.NetHandlerPlayServer.func_147346_a(NetHandlerPlayServer.java:539)
at net.minecraft.network.play.client.C08PacketPlayerBlockPlacement.func_148833_a(SourceFile:60)
at net.minecraft.network.play.client.C08PacketPlayerBlockPlacement.func_148833_a(SourceFile:9)
at net.minecraft.network.NetworkManager.func_74428_b(NetworkManager.java:212)
at net.minecraft.network.NetworkSystem.func_151269_c(NetworkSystem.java:165)
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:659)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:547)
at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:111)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:427)
at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:685)

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

-- Head --
Stacktrace:
at java.util.Random.nextInt(Unknown Source)
at net.minecraftforge.common.ChestGenHooks.generateStacks(ChestGenHooks.java:111)
at mal.lootbags.LootMap.getRandomItem(LootMap.java:404)
at mal.lootbags.item.LootbagItem.getLootItem(LootbagItem.java:397)
at mal.lootbags.item.LootbagItem.getLootItem(LootbagItem.java:326)
at mal.lootbags.item.LootbagItem.generateInventory(LootbagItem.java:304)
at mal.lootbags.item.LootbagItem.func_77659_a(LootbagItem.java:524)
at net.minecraft.item.ItemStack.func_77957_a(ItemStack.java:146)
at net.minecraft.server.management.ItemInWorldManager.func_73085_a(ItemInWorldManager.java:316)
at net.minecraft.network.NetHandlerPlayServer.func_147346_a(NetHandlerPlayServer.java:539)
at net.minecraft.network.play.client.C08PacketPlayerBlockPlacement.func_148833_a(SourceFile:60)
at net.minecraft.network.play.client.C08PacketPlayerBlockPlacement.func_148833_a(SourceFile:9)
at net.minecraft.network.NetworkManager.func_74428_b(NetworkManager.java:212)

-- Ticking connection --
Details:
Connection: net.minecraft.network.NetworkManager@4b146ff1
Stacktrace:
at net.minecraft.network.NetworkSystem.func_151269_c(NetworkSystem.java:165)
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:659)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:547)
at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:111)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:427)
at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:685)

-- System Details --
Details:
Minecraft Version: 1.7.10
Operating System: Windows 7 (amd64) version 6.1
Java Version: 1.8.0_65, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 142100456 bytes (135 MB) / 619184128 bytes (590 MB) up to 1521483776 bytes (1451 MB)
JVM Flags: 3 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1536M -Xmn256M
AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
FML: MCP v9.05 FML v7.10.99.99 Minecraft Forge 10.13.4.1492 45 mods loaded, 45 mods active
States: 'U' = Unloaded 'L' = Loaded 'C' = Constructed 'H' = Pre-initialized 'I' = Initialized 'J' = Post-initialized 'A' = Available 'D' = Disabled 'E' = Errored
UCHIJAAAA mcp{9.05} Minecraft Coder Pack
UCHIJAAAA FML{7.10.99.99} Forge Mod Loader
UCHIJAAAA Forge{10.13.4.1492} Minecraft Forge
UCHIJAAAA PlayerAPI{1.2} Player API
UCHIJAAAA DamageIndicatorsMod{3.2.0} Damage Indicators
UCHIJAAAA MovingWorld{1.7.10-1.8} Moving World
UCHIJAAAA ArchimedesShipsPlus{1.7.10-1.8} Archimedes' Ships Plus
UCHIJAAAA armourersWorkshop{1.7.10-0.31.2.82} Armourer's Workshop
UCHIJAAAA Backpack{2.0.1} Backpack
UCHIJAAAA bettervillages{0.4} Better Villages Mod
UCHIJAAAA BuildCraft|Core{6.3.7} BuildCraft
UCHIJAAAA BuildCraft|Transport{6.3.7} BC Transport
UCHIJAAAA BuildCraft|Silicon{6.3.7} BC Silicon
UCHIJAAAA BuildCraft|Builders{6.3.7} BC Builders
UCHIJAAAA BuildCraft|Energy{6.3.7} BC Energy
UCHIJAAAA BuildCraft|Factory{6.3.7} BC Factory
UCHIJAAAA craftguide{1.6.8.2} CraftGuide
UCHIJAAAA exnihilo{1.38-48} Ex Nihilo
UCHIJAAAA MetallurgyCore{4.0.4} Metallurgy Core
UCHIJAAAA Mantle{1.7.10-0.3.2.jenkins191} Mantle
UCHIJAAAA TConstruct{1.7.10-1.8.8.build988} Tinkers' Construct
UCHIJAAAA Metallurgy{4.0.8} Metallurgy 4
UCHIJAAAA exastrisrebirth{MC1.7.10-1.01-45} Ex Astris Rebirth
UCHIJAAAA ExtraTiC{1.4.5} ExtraTiC
UCHIJAAAA rftl{1.7.10} [Rotten Flesh to Leather](Forge SSP SMP - Rotten Flesh 1.7.2 1.7.10.jar)
UCHIJAAAA iChunUtil{4.2.2} iChunUtil
UCHIJAAAA GraviGun{4.0.0-beta} GraviGun
UCHIJAAAA Hats{4.0.1} Hats
UCHIJAAAA levelup{0.10} Level Up!
UCHIJAAAA lootbags{1.8.1} Loot Bags
UCHIJAAAA RadixCore{2.1.0} RadixCore
UCHIJAAAA MCA{1.7.10-5.1.0} Minecraft Comes Alive
UCHIJAAAA mochickens{1.6.1} Mo Chickens
UCHIJAAAA Ping{%MOD_VERSION} Ping
UCHIJAAAA primitivemobs{1.0} Primitive Mobs
UCHIJAAAA quiverchevsky{b100} QuiverBow
UCHIJAAAA Roguelike{1.3.5} Roguelike Dungeons
UCHIJAAAA AS_Ruins{14.6} Ruins Spawning System
UCHIJAAAA secretroomsmod{4.7.1} The SecretRoomsMod
UCHIJAAAA SpecialMobs{3.0.3} Special Mobs
UCHIJAAAA SwordPedestal{1.1(1.7.10)} Sword Pedestal
UCHIJAAAA TKE{2.3} The Kappa Experience
UCHIJAAAA TooMuchTNT{2.9} [TooMuchTNT](TooMuchTNT v2.9.jar.zip)
UCHIJAAAA TragicMC{2.44.2776 Beta} TragicMC 2
UCHIJAAAA IguanaTweaksTConstruct{1.7.10-2.1.5.140} Iguana Tinker Tweaks
GL info: ERROR RuntimeException: No OpenGL context found in the current thread.
Mantle Environment: Environment healthy.
TConstruct Environment: Environment healthy.
Profiler Position: N/A (disabled)
Vec3 Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
Player Count: 1 / 8; [EntityPlayerMP['red3dred'/71, l='New World', x=249,01, y=4,00, z=-1090,57]]
Type: Integrated Server (map_client.txt)
Is Modded: Definitely; Client brand changed to 'fml,forge'

I attempted clearing all ChestGenHooks from the config and that didn't solve anything. Just pointing that out, in case it may help.

Can you post the config as well? I recall there being a similar crash, but I don't remember what caused it. I know an error in the config causes that crash, and I think there was a mod that had malformed loot table entries, but both cases cause crashes in singleplayer as well. I can't offer much more help right now than find what the item(s) are and take them out of the config for now, I'm in the middle of rewriting the mod (slowly).