Tinkers construct mods Forge test

A detailed walkthrough of the error, its code path and all known details is as follows:
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-- Head --
Stacktrace:
	at tconstruct.client.tabs.InventoryTabKnapsack.shouldAddToList(InventoryTabKnapsack.java:23)
	at tconstruct.client.tabs.TabRegistry.updateTabValues(TabRegistry.java:64)
	at tconstruct.client.tabs.TabRegistry.guiPostInit(TabRegistry.java:43)
	at cpw.mods.fml.common.eventhandler.ASMEventHandler_28_TabRegistry_guiPostInit_Post.invoke(.dynamic)
	at cpw.mods.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:54)
	at cpw.mods.fml.common.eventhandler.EventBus.post(EventBus.java:138)
	at net.minecraft.client.gui.GuiScreen.func_146280_a(GuiScreen.java:257)
	at net.minecraft.client.Minecraft.func_147108_a(Minecraft.java:808)

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [EntityClientPlayerMP['Buzzi'/0, l='MpServer', x=1452.15, y=2.62, z=-1680.37]]
	Chunk stats: MultiplayerChunkCache: 441, 441
	Level seed: 0
	Level generator: ID 01 - flat, ver 0. Features enabled: false
	Level generator options:
	Level spawn location: World: (1461,4,-1683), Chunk: (at 5,0,13 in 91,-106; contains blocks 1456,0,-1696 to 1471,255,-1681), Region: (2,-4; contains chunks 64,-128 to 95,-97, blocks 1024,0,-2048 to 1535,255,-1537)
	Level time: 544 game time, 544 day time
	Level dimension: 0
	Level storage version: 0x00000 - Unknown?
	Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
	Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: false
	Forced entities: 1 total; [EntityClientPlayerMP['Buzzi'/0, l='MpServer', x=1452.15, y=2.62, z=-1680.37]]
	Retry entities: 0 total; []
	Server brand: BungeeCord (git:BungeeCord-Bootstrap:1.8-SNAPSHOT:"cc3a8c0":1071) <- Spigot
	Server type: Non-integrated multiplayer server
Stacktrace:
	at net.minecraft.client.multiplayer.WorldClient.func_72914_a(WorldClient.java:373)
	at net.minecraft.client.Minecraft.func_71396_d(Minecraft.java:2444)
	at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:927)
	at net.minecraft.client.main.Main.main(SourceFile:148)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:483)
	at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
	at net.minecraft.launchwrapper.Launch.main(Launch.java:28)