Minecraft Multiplayer crash: Rendering Item

When i was in a server, building, a guy said my name and then my game crashed. here is the inform:
---- Minecraft Crash Report ----
// On the bright side, I bought you a teddy bear!

Time: 01/08/15 18:29
Description: Rendering item

com.google.common.util.concurrent.UncheckedExecutionException: java.lang.NullPointerException
at com.google.common.cache.LocalCache$Segment.get(LocalCache.java:2201)
at com.google.common.cache.LocalCache.get(LocalCache.java:3934)
at com.google.common.cache.LocalCache.getOrLoad(LocalCache.java:3938)
at com.google.common.cache.LocalCache$LocalLoadingCache.get(LocalCache.java:4821)
at com.google.common.cache.LocalCache$LocalLoadingCache.getUnchecked(LocalCache.java:4827)
at bnp.a(SourceFile:126)
at bhk.a(SourceFile:76)
at bfi.a(SourceFile:52)
at bjh.a(SourceFile:122)
at bjh.a(SourceFile:323)
at bjh.b(SourceFile:359)
at avo.a(SourceFile:880)
at avo.a(SourceFile:336)
at avo.a(SourceFile:144)
at bfk.a(SourceFile:1021)
at ave.av(SourceFile:915)
at ave.a(SourceFile:325)
at net.minecraft.client.main.Main.main(SourceFile:124)
Caused by: java.lang.NullPointerException
at com.mojang.authlib.yggdrasil.YggdrasilMinecraftSessionService.getTextures(YggdrasilMinecraftSessionService.java:144)
at bnp$1.a(SourceFile:47)
at bnp$1.load(SourceFile:44)
at com.google.common.cache.LocalCache$LoadingValueReference.loadFuture(LocalCache.java:3524)
at com.google.common.cache.LocalCache$Segment.loadSync(LocalCache.java:2317)
at com.google.common.cache.LocalCache$Segment.lockedGetOrLoad(LocalCache.java:2280)
at com.google.common.cache.LocalCache$Segment.get(LocalCache.java:2195)
... 17 more

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

– Head –
Stacktrace:
at com.google.common.cache.LocalCache$Segment.get(LocalCache.java:2201)
at com.google.common.cache.LocalCache.get(LocalCache.java:3934)
at com.google.common.cache.LocalCache.getOrLoad(LocalCache.java:3938)
at com.google.common.cache.LocalCache$LocalLoadingCache.get(LocalCache.java:4821)
at com.google.common.cache.LocalCache$LocalLoadingCache.getUnchecked(LocalCache.java:4827)
at bnp.a(SourceFile:126)
at bhk.a(SourceFile:76)
at bfi.a(SourceFile:52)
at bjh.a(SourceFile:122)
at bjh.a(SourceFile:323)

– Item being rendered –
Details:
Item Type: aat@2a87ba34
Item Aux: 3
Item NBT: {SkullOwner:{Id:"c8688610-bbb2-4687-bff8-937e07ff2433",Properties:{textures:[0:

{Value:""}

]}}}
Item Foil: false
Stacktrace:
at bjh.b(SourceFile:359)
at avo.a(SourceFile:880)
at avo.a(SourceFile:336)
at avo.a(SourceFile:144)

– Affected level –
Details:
Level name: MpServer
All players: 1 total; [bew['_DatLaunchedGuy_'/1780, l='MpServer', x=4588,81, y=65,00, z=7996,65]]
Chunk stats: MultiplayerChunkCache: 60, 60
Level seed: 0
Level generator: ID 00 - default, ver 1. Features enabled: false
Level generator options:
Level spawn location: 5982,00,70,00,-1195,00 - World: (5982,70,-1195), Chunk: (at 14,4,5 in 373,-75; contains blocks 5968,0,-1200 to 5983,255,-1185), Region: (11,-3; contains chunks 352,-96 to 383,-65, blocks 5632,0,-1536 to 6143,255,-1025)
Level time: 257139655 game time, 52338221 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
Forced entities: 1 total; [bew['_DatLaunchedGuy_'/1780, l='MpServer', x=4588,81, y=65,00, z=7996,65]]
Retry entities: 0 total; []
Server brand: BungeeCord (git:BungeeCord-Bootstrap:1.8-SNAPSHOT:"6343416":1076) <- Spigot
Server type: Non-integrated multiplayer server
Stacktrace:
at bdb.a(SourceFile:309)
at ave.b(SourceFile:2311)
at ave.a(SourceFile:334)
at net.minecraft.client.main.Main.main(SourceFile:124)

– System Details –
Details:
Minecraft Version: 1.8.8
Operating System: Mac OS X (x86_64) version 10.11
Java Version: 1.8.0_51, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 191716584 bytes (182 MB) / 362373120 bytes (345 MB) up to 1060372480 bytes (1011 MB)
JVM Flags: 5 total; -Xmx1G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
Launched Version: 1.8.8
LWJGL: 2.9.2
OpenGL: AMD Radeon HD 6750M OpenGL Engine GL version 2.1 ATI-1.36.33, ATI Technologies 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: English (US)
Profiler Position: N/A (disabled)
CPU: 4x Intel(R) Core(TM) i5-2400S CPU @ 2.50GHz
Hope u help me fix this.