---- Minecraft Crash Report ----
// But it works on my machine.

Time: 3/09/15 10:52 AM
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 xx$b.b(SourceFile:430)
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 xx$b.b(SourceFile:430)
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: 28895
Entity Name: Enderman
Entity's Exact location: -205.86, 70.00, 536.45
Entity's Block location: -206.00,70.00,536.00 - World: (-206,70,536), Chunk: (at 2,4,8 in -13,33; contains blocks -208,0,528 to -193,255,543), Region: (-1,1; contains chunks -32,32 to -1,63, blocks -512,0,512 to -1,255,1023)
Entity's Momentum: 0.00, -0.08, 0.00
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: 15w36b
All players: 1 total; [ln['FunBandit29'/636, l='15w36b', x=-201.72, y=71.00, z=531.20]]
Chunk stats: ServerChunkCache: 4247 Drop: 0
Level seed: 3716809166385961710
Level generator: ID 00 - default, ver 1. Features enabled: true
Level generator options:
Level spawn location: -211.00,64.00,527.00 - World: (-211,64,527), Chunk: (at 13,4,15 in -14,32; contains blocks -224,0,512 to -209,255,527), Region: (-1,1; contains chunks -32,32 to -1,63, blocks -512,0,512 to -1,255,1023)
Level time: 10748 game time, 10748 day time
Level dimension: 0
Level storage version: 0x04ABD - Anvil
Level weather: Rain time: 144302 (now: false), thunder time: 159803 (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 7 (amd64) version 6.1
Java Version: 1.8.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 3832172632 bytes (3654 MB) / 5768867840 bytes (5501 MB) up to 6979321856 bytes (6656 MB)
JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx7G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn5G
IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
Profiler Position: N/A (disabled)
Player Count: 1 / 8; [ln['FunBandit29'/636, l='15w36b', x=-201.72, y=71.00, z=531.20]]
Type: Integrated Server (map_client.txt)
Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.