Crash

---- Minecraft Crash Report ----
// Why did you do that?

Time: 2-9-15 17:48
Description: Ticking entity

java.lang.IllegalArgumentException: Modifier is already applied on this attribute!
	at ry.b(SourceFile:89)
	at xx.c(SourceFile:123)
	at ul.b(SourceFile:82)
	at su.a(SourceFile:135)
	at su.a(SourceFile:107)
	at rl.bT(SourceFile:547)
	at rk.n(SourceFile:1602)
	at rl.n(SourceFile:404)
	at ye.n(SourceFile:33)
	at xx.n(SourceFile:211)
	at rk.m(SourceFile:1470)
	at rl.m(SourceFile:243)
	at ye.m(SourceFile:38)
	at agq.a(SourceFile:1436)
	at ll.a(SourceFile:661)
	at agq.g(SourceFile:1414)
	at agq.k(SourceFile:1305)
	at ll.k(SourceFile:540)
	at net.minecraft.server.MinecraftServer.D(SourceFile:625)
	at net.minecraft.server.MinecraftServer.C(SourceFile:553)
	at bvd.C(SourceFile:154)
	at net.minecraft.server.MinecraftServer.run(SourceFile:457)
	at java.lang.Thread.run(Thread.java:745)


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

-- Head --
Stacktrace:
	at ry.b(SourceFile:89)
	at xx.c(SourceFile:123)
	at ul.b(SourceFile:82)
	at su.a(SourceFile:135)
	at su.a(SourceFile:107)
	at rl.bT(SourceFile:547)
	at rk.n(SourceFile:1602)
	at rl.n(SourceFile:404)
	at ye.n(SourceFile:33)
	at xx.n(SourceFile:211)
	at rk.m(SourceFile:1470)
	at rl.m(SourceFile:243)
	at ye.m(SourceFile:38)
	at agq.a(SourceFile:1436)
	at ll.a(SourceFile:661)
	at agq.g(SourceFile:1414)

-- Entity being ticked --
Details:
	Entity Type: Enderman (xx)
	Entity ID: 6103
	Entity Name: Enderman
	Entity's Exact location: 5,93, 65,36, 272,46
	Entity's Block location: 5,00,65,00,272,00 - World: (5,65,272), Chunk: (at 5,4,0 in 0,17; contains blocks 0,0,272 to 15,255,287), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
	Entity's Momentum: 0,24, 0,28, -0,02
	Entity's Rider: ~~ERROR~~ NullPointerException: null
	Entity's Vehicle: ~~ERROR~~ NullPointerException: null
Stacktrace:
	at agq.k(SourceFile:1305)
	at ll.k(SourceFile:540)

-- Affected level --
Details:
	Level name: New World
	All players: 1 total; [ln['LennartPS'/244, l='New World', x=3,10, y=65,00, z=271,58]]
	Chunk stats: ServerChunkCache: 268 Drop: 0
	Level seed: -915112182000071490
	Level generator: ID 00 - default, ver 1. Features enabled: true
	Level generator options:
	Level spawn location: 4,00,64,00,252,00 - World: (4,64,252), Chunk: (at 4,4,12 in 0,15; contains blocks 0,0,240 to 15,255,255), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
	Level time: 2457 game time, 2457 day time
	Level dimension: 0
	Level storage version: 0x04ABD - Anvil
	Level weather: Rain time: 24781 (now: false), thunder time: 85058 (now: false)
	Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: true
Stacktrace:
	at net.minecraft.server.MinecraftServer.D(SourceFile:625)
	at net.minecraft.server.MinecraftServer.C(SourceFile:553)
	at bvd.C(SourceFile:154)
	at net.minecraft.server.MinecraftServer.run(SourceFile:457)
	at java.lang.Thread.run(Thread.java:745)

-- System Details --
Details:
	Minecraft Version: 15w36b
	Operating System: Windows 8.1 (amd64) version 6.3
	Java Version: 1.8.0_25, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 257594824 bytes (245 MB) / 417841152 bytes (398 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: 13, tallocated: 95
	Profiler Position: N/A (disabled)
	Player Count: 1 / 8; [ln['LennartPS'/244, l='New World', x=3,10, y=65,00, z=271,58]]
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.