Put the summary of the bug you're having here

When playing Minecraft on 'mc.slabcraft.net' 's SkyWars,
Minecraft crashes everytime I open a chest,
message reads "NPE: Invalid item data (MS) ...an item with invalid data was attempted to be loaded..."
See crash report below:
---- Minecraft Crash Report ----
// My bad.

Time: 9/2/14 3:05 PM
Description: Rendering item

java.lang.NullPointerException: Rendering item
at amj.t(SourceFile:666)
at cqh.a(SourceFile:124)
at cqh.a(SourceFile:335)
at cqh.b(SourceFile:371)
at byl.a(SourceFile:249)
at byl.a(SourceFile:107)
at cji.b(SourceFile:1020)
at bsu.as(SourceFile:903)
at bsu.a(SourceFile:314)
at net.minecraft.client.main.Main.main(SourceFile:120)

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

– Head –
Stacktrace:
at amj.t(SourceFile:666)
at cqh.a(SourceFile:124)
at cqh.a(SourceFile:335)

– Item being rendered –
Details:
Item Type: null
Item Aux: 0
Item NBT: null
Item Foil: ~_ERROR~ NullPointerException: null
Stacktrace:
at cqh.b(SourceFile:371)
at byl.a(SourceFile:249)
at byl.a(SourceFile:107)

– Screen render details –
Details:
Screen name: byw
Mouse location: Scaled: (231, 186). Absolute: (695, 193)
Screen size: Scaled: (427, 251). Absolute: (1280, 752). Scale factor of 3

– Affected level –
Details:
Level name: MpServer
All players: 5 total; [cio['mattkobe'/300620, l='MpServer', x=1002.76, y=119.00, z=14888.09], cip['emg_01'/145701, l='MpServer', x=1004.53, y=51.00, z=14896.97], cip['whiterunsthane'/131099, l='MpServer', x=1007.13, y=51.00, z=14869.63], cip['glenroy007'/134089, l='MpServer', x=968.69, y=119.00, z=14917.84], cip['DarthVancent'/145009, l='MpServer', x=978.38, y=51.00, z=14882.88]]
Chunk stats: MultiplayerChunkCache: 441, 441
Level seed: 0
Level generator: ID 00 - default, ver 1. Features enabled: false
Level generator options:
Level spawn location: 0.00,64.00,0.00 - World: (0,64,0), Chunk: (at 0,4,0 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: 655191 game time, 157230083 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: 16 total; [cip['glenroy007'/134089, l='MpServer', x=968.69, y=119.00, z=14917.84], cip['emg_01'/145701, l='MpServer', x=1004.53, y=51.00, z=14896.97], adw['item.tile.flower2.poppy'/147429, l='MpServer', x=1009.66, y=51.00, z=14891.34], cip['glenroy007'/134089, l='MpServer', x=968.69, y=119.00, z=14917.84], cip['SillyBilly404'/147040, l='MpServer', x=1008.59, y=118.00, z=14855.00], cip['DarthVancent'/145009, l='MpServer', x=978.38, y=51.00, z=14882.88], cio['mattkobe'/300620, l='MpServer', x=1002.76, y=119.00, z=14888.09], adw['item.tile.flower2.poppy'/147370, l='MpServer', x=1005.47, y=50.00, z=14898.31], cip['whiterunsthane'/131099, l='MpServer', x=1007.13, y=51.00, z=14869.63], cip['emg_01'/145701, l='MpServer', x=1004.53, y=51.00, z=14896.97], adw['item.item.wheat'/147055, l='MpServer', x=1004.00, y=51.00, z=14868.16], cip['THRIFTSHOP1175'/133231, l='MpServer', x=981.06, y=50.00, z=14843.44], cip['whiterunsthane'/131099, l='MpServer', x=1007.13, y=51.00, z=14869.63], adw['item.tile.flower1.dandelion'/147357, l='MpServer', x=1001.25, y=51.00, z=14895.69], cip['DarthVancent'/145009, l='MpServer', x=978.38, y=51.00, z=14882.88], adw['item.tile.cloth.yellow'/147514, l='MpServer', x=1003.88, y=117.88, z=14887.88]]
Retry entities: 0 total; []
Server brand: ungeeCord (git:BungeeCord-Bootstrap:1.8-SNAPSHOT:"73d7e0c":993) <-
Server type: Non-integrated multiplayer server
Stacktrace:
at cen.a(SourceFile:308)
at bsu.b(SourceFile:2252)
at bsu.a(SourceFile:323)
at net.minecraft.client.main.Main.main(SourceFile:120)

– System Details –
Details:
Minecraft Version: 1.8
Operating System: Mac OS X (x86_64) version 10.7.5
Java Version: 1.6.0_65, Apple Inc.
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Apple Inc.
Memory: 100905480 bytes (96 MB) / 273297408 bytes (260 MB) up to 1060372480 bytes (1011 MB)
JVM Flags: 5 total; -Xmx1G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
IntCache: cache: 0, tcache: 54, allocated: 13, tallocated: 95
Launched Version: 1.8
LWJGL: 2.9.2
OpenGL: Intel HD Graphics 3000 OpenGL Engine GL version 2.1 APPLE-7.32.12, Intel Inc.
GL Caps: Using GL 1.3 multitexturing.
Using GL 1.3 texture combiners.
Using framebuffer objects because ARB_framebuffer_object is supported and separate blending is supported.
Shaders are available because OpenGL 2.1 is supported.
VBOs are available because OpenGL 1.5 is supported.

Using VBOs: No
Is Modded: Probably not. Jar signature remains and client brand is untouched.
Type: Client (map_client.txt)
Resource Packs: []
Current Language: Canadian English (Canada)
Profiler Position: N/A (disabled)