Minecraft - Command causes Minecraft to crash

I can't get into my world because I typed a command in the command block that can give me a custom head, but the game crashed.

This is the crash report:

---- Minecraft Crash Report ----
// Sorry :(

Time: 6/4/16 4:34 PM
Description: Loading entity NBT

java.lang.NullPointerException: Loading entity NBT
    at com.mojang.authlib.yggdrasil.YggdrasilGameProfileRepository.findProfilesByNames(YggdrasilGameProfileRepository.java:53)
    at mj.a(SourceFile:80)
    at mj.a(SourceFile:141)
    at aqo.b(SourceFile:139)
    at aeq.a(SourceFile:135)
    at adq.c(SourceFile:175)
    at adq.a(SourceFile:112)
    at zi.b(SourceFile:460)
    at zj.a(SourceFile:771)
    at ls.a(SourceFile:171)
    at rr.f(SourceFile:1394)
    at mn.a(SourceFile:289)
    at mn.a(SourceFile:118)
    at me.b(SourceFile:116)
    at me.c(SourceFile:62)
    at em.a(SourceFile:232)
    at mb.c(SourceFile:187)
    at net.minecraft.server.MinecraftServer.D(SourceFile:644)
    at net.minecraft.server.MinecraftServer.C(SourceFile:554)
    at byl.C(SourceFile:155)
    at net.minecraft.server.MinecraftServer.run(SourceFile:458)
    at java.lang.Thread.run(Unknown Source)


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

-- Head --
Thread: Server thread
Stacktrace:
    at com.mojang.authlib.yggdrasil.YggdrasilGameProfileRepository.findProfilesByNames(YggdrasilGameProfileRepository.java:53)
    at mj.a(SourceFile:80)
    at mj.a(SourceFile:141)
    at aqo.b(SourceFile:139)
    at aeq.a(SourceFile:135)
    at adq.c(SourceFile:175)
    at adq.a(SourceFile:112)
    at zi.b(SourceFile:460)
    at zj.a(SourceFile:771)
    at ls.a(SourceFile:171)

-- Entity being loaded --
Details:
    Entity Type: null (ls)
    Entity ID: 75
    Entity Name: TykesTPO
    Entity's Exact location: 86.89, 32.00, 289.36
    Entity's Block location: World: (86,32,289), Chunk: (at 6,2,1 in 5,18; contains blocks 80,0,288 to 95,255,303), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
    Entity's Momentum: 0.00, -0.08, 0.00
    Entity's Passengers: []
    Entity's Vehicle: ~~ERROR~~ NullPointerException: null
Stacktrace:
    at rr.f(SourceFile:1394)
    at mn.a(SourceFile:289)
    at mn.a(SourceFile:118)
    at me.b(SourceFile:116)
    at me.c(SourceFile:62)
    at em.a(SourceFile:232)

-- Ticking connection --
Details:
    Connection: em@13093da
Stacktrace:
    at mb.c(SourceFile:187)
    at net.minecraft.server.MinecraftServer.D(SourceFile:644)
    at net.minecraft.server.MinecraftServer.C(SourceFile:554)
    at byl.C(SourceFile:155)
    at net.minecraft.server.MinecraftServer.run(SourceFile:458)
    at java.lang.Thread.run(Unknown Source)

-- System Details --
Details:
    Minecraft Version: 1.9.4
    Operating System: Windows 7 (x86) version 6.1
    Java Version: 1.8.0_92, Oracle Corporation
    Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Oracle Corporation
    Memory: 57135896 bytes (54 MB) / 175489024 bytes (167 MB) up to 1037959168 bytes (989 MB)
    JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
    IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
    Profiler Position: N/A (disabled)
    Player Count: 0 / 8; []
    Type: Integrated Server (map_client.txt)
    Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.