put this in a command block {SkullOwner:... and cant join

{SkullOwner:{Id:"7d3ad43e-ead4-4248-8c3c-484452db4438",Properties:{textures:[0:{Value:"eyJ0ZXh0dXJlcyI6eyJTS0lOIjp7InVybCI6IiJ9fX0=",},],},},display:{Name:"Taco",},} 

---- Minecraft Crash Report ----
// Ouch. That hurt :(

Time: 8/3/15 4:39 PM
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$LocalLoadingCache.getUnchecked(LocalCache.java:4827)
	at cvw.a(SourceFile:124)
	at cnw.a(SourceFile:76)
	at cjd.a(SourceFile:52)
	at cqh.a(SourceFile:119)
	at cqh.a(SourceFile:335)
	at cqh.b(SourceFile:371)
	at btz.a(SourceFile:878)
	at btz.a(SourceFile:334)
	at btz.a(SourceFile:142)
	at cji.b(SourceFile:1002)
	at bsu.as(SourceFile:903)
	at bsu.a(SourceFile:314)
	at net.minecraft.client.main.Main.main(SourceFile:120)
Caused by: java.lang.NullPointerException
	at com.mojang.authlib.yggdrasil.YggdrasilMinecraftSessionService.isWhitelistedDomain(YggdrasilMinecraftSessionService.java:210)
	at com.mojang.authlib.yggdrasil.YggdrasilMinecraftSessionService.getTextures(YggdrasilMinecraftSessionService.java:149)
	at cvx.a(SourceFile:47)
	at cvx.load(SourceFile:44)
	at com.google.common.cache.LocalCache$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 cvw.a(SourceFile:124)
	at cnw.a(SourceFile:76)
	at cjd.a(SourceFile:52)
	at cqh.a(SourceFile:119)
	at cqh.a(SourceFile:335)

-- Item being rendered --
Details:
	Item Type: anh@5f025000
	Item Aux: 3
	Item NBT: {SkullOwner:{Id:"7d3ad43e-ead4-4248-8c3c-484452db4438",Properties:{textures:[0:{Value:"eyJ0ZXh0dXJlcyI6eyJTS0lOIjp7InVybCI6IiJ9fX0=",},],},},display:{Name:"Taco",},}
	Item Foil: false
Stacktrace:
	at cqh.b(SourceFile:371)
	at btz.a(SourceFile:878)
	at btz.a(SourceFile:334)
	at btz.a(SourceFile:142)

-- Affected level --
Details:
	Level name: MpServer
	All players: 2 total; [cio['ElianaPlaysMc'/3893912, l='MpServer', x=1209.70, y=56.00, z=3.40], cip['Donald Duck'/3893913, l='MpServer', x=1193.88, y=57.00, z=29.19]]
	Chunk stats: MultiplayerChunkCache: 250, 250
	Level seed: 0
	Level generator: ID 01 - flat, ver 0. Features enabled: false
	Level generator options: 
	Level spawn location: 1354.00,57.00,-153.00 - World: (1354,57,-153), Chunk: (at 10,3,7 in 84,-10; contains blocks 1344,0,-160 to 1359,255,-145), Region: (2,-1; contains chunks 64,-32 to 95,-1, blocks 1024,0,-512 to 1535,255,-1)
	Level time: 6538775 game time, 7572072 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: 3 total; [cio['ElianaPlaysMc'/3893912, l='MpServer', x=1209.70, y=56.00, z=3.40], cip['Donald Duck'/3893913, l='MpServer', x=1193.88, y=57.00, z=29.19], cip['Donald Duck'/3893913, l='MpServer', x=1193.88, y=57.00, z=29.19]]
	Retry entities: 0 total; []
	Server brand: Spigot
	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: 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: 101103272 bytes (96 MB) / 240816128 bytes (229 MB) up to 1060372480 bytes (1011 MB)
	JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	Launched Version: 1.8
	LWJGL: 2.9.1
	OpenGL: Intel(R) HD Graphics 4000 GL version 4.0.0 - Build 9.17.10.3114, Intel
	GL Caps: Using GL 1.3 multitexturing.
Using GL 1.3 texture combiners.
Using framebuffer objects because OpenGL 3.0 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: [Faithful_4.zip]
	Current Language: English (US)
	Profiler Position: N/A (disabled)