everytime i try to put on the backpack minecraft crashes heres the crash report
---- Minecraft Crash Report ----
// My bad.

Time: 12/2/15 7:08 PM
Description: Unexpected error

java.lang.NullPointerException: Unexpected error
at net.minecraft.crash.CrashReportCategory.func_85069_a(CrashReportCategory.java:145)
at net.minecraft.crash.CrashReport.func_85057_a(CrashReport.java:333)
at net.minecraft.crash.CrashReport.func_85058_a(CrashReport.java:303)
at net.minecraft.client.Minecraft.func_71407_l(Unknown Source)
at net.minecraft.client.Minecraft.func_71411_J(Unknown Source)
at net.minecraft.client.Minecraft.func_99999_d(Unknown Source)
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)

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

-- Head --
Stacktrace:
at net.minecraft.crash.CrashReportCategory.func_85069_a(CrashReportCategory.java:145)
at net.minecraft.crash.CrashReport.func_85057_a(CrashReport.java:333)
at net.minecraft.crash.CrashReport.func_85058_a(CrashReport.java:303)

-- Affected level --
Details:
Level name: MpServer
All players: 1 total; [EntityClientPlayerMP['Barsam'/94, l='MpServer', x=119.43, y=86.29, z=379.08]]
Chunk stats: MultiplayerChunkCache: 441, 441
Level seed: 0
Level generator: ID 00 - default, ver 1. Features enabled: false
Level generator options:
Level spawn location: World: (354,63,494), Chunk: (at 2,3,14 in 22,30; contains blocks 352,0,480 to 367,255,495), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Level time: 126067966 game time, 127003882 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: creative (ID 1). Hardcore: false. Cheats: false

Stacktrace:
at net.minecraft.client.multiplayer.WorldClient.func_72914_a(WorldClient.java:373)
at net.minecraft.client.Minecraft.func_71396_d(Unknown Source)
at net.minecraft.client.Minecraft.func_99999_d(Unknown Source)
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)

-- System Details --
Details:
Minecraft Version: 1.7.10
Operating System: Windows 8 (amd64) version 6.2
Java Version: 1.8.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 195309232 bytes (186 MB) / 454815744 bytes (433 MB) up to 3207856128 bytes (3059 MB)
JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx3G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
IntCache: cache: 0, tcache: 0, allocated: 12, tallocated: 94
FML: MCP v9.05 FML v7.10.99.99 Minecraft Forge 10.13.4.1448 7 mods loaded, 7 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{10.13.4.1448} Minecraft Forge
UCHIJAAAA battlegear2{1.7.10} Mine & Blade Battlegear 2 - Bullseye
UCHIJAAAA adventurebackpack{1.7.10-0.8b} Adventure Backpack
UCHIJAAAA AssassinCraft{r130f} AssassinCraft
UCHIJAAAA customnpcs{1.7.10} CustomNpcs
GL info: ' Vendor: 'Intel' Version: '4.0.0 - Build 9.18.10.3071' Renderer: 'Intel(R) HD Graphics 4400'
Launched Version: 1.7.10-Forge10.13.4.1448-1.7.10
LWJGL: 2.9.1
OpenGL: Intel(R) HD Graphics 4400 GL version 4.0.0 - Build 9.18.10.3071, Intel
GL Caps: Using GL 1.3 multitexturing.
Using framebuffer objects because OpenGL 3.0 is supported and separate blending is supported.
Anisotropic filtering is supported and maximum anisotropy is 16.
Shaders are available because OpenGL 2.1 is supported.

Is Modded: Definitely; Client brand changed to 'fml,forge'
Type: Client (map_client.txt)
Resource Packs: []
Current Language: Canadian English (Canada)
Profiler Position: N/A (disabled)
Vec3 Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
Anisotropic Filtering: Off (1)

You're using an old version.