Hopper: java.lang.IllegalArgumentException: Modifier name cannot be empty

This is an automatically generated report based from the following crash: http://hopper.minecraft.net/crashes/minecraft/MCX-145924/

Crash:

java.lang.IllegalArgumentException: Modifier name cannot be empty
	at org.apache.commons.lang3.Validate.notEmpty(Validate.java:398)
	at pr.<init>(SourceFile:31)
	at up.a(SourceFile:92)
	at zg.D(SourceFile:595)
	at pd.h(SourceFile:1192)
	at vf.h(SourceFile:205)

The following is the first clean report made public about this crash:

---- Minecraft Crash Report ----
// I blame Dinnerbone.

Time: 13/09/14 15:42
Description: Ticking player

java.lang.IllegalArgumentException: Modifier name cannot be empty
	at org.apache.commons.lang3.Validate.notEmpty(Validate.java:398)
	at pr.<init>(SourceFile:31)
	at up.a(SourceFile:92)
	at zg.D(SourceFile:595)
	at pd.h(SourceFile:1192)
	at vf.h(SourceFile:205)
	at kp.i(SourceFile:197)
	at ku.a(SourceFile:195)
	at gm.a(SourceFile:136)
	at ea.b(SourceFile:64)
	at ku.e(SourceFile:63)
	at kx.b(SourceFile:37)
	at boc.b(SourceFile:84)
	at net.minecraft.server.MinecraftServer.u(SourceFile:483)
	at net.minecraft.server.MinecraftServer.t(SourceFile:400)
	at bnz.t(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:334)
	at jb.run(SourceFile:577)


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

-- Head --
Stacktrace:
	at org.apache.commons.lang3.Validate.notEmpty(Validate.java:398)
	at pr.<init>(SourceFile:31)
	at up.a(SourceFile:92)
	at zg.D(SourceFile:595)
	at pd.h(SourceFile:1192)
	at vf.h(SourceFile:205)

-- Player being ticked --
Details:
	Entity Type: null (kp)
	Entity ID: 6
	Entity Name: CASTORgemini
	Entity's Exact location: -36.49, 4.00, -22.53
	Entity's Block location: World: (-37,4,-23), Chunk: (at 11,0,9 in -3,-2; contains blocks -48,0,-32 to -33,255,-17), Region: (-1,-1; contains chunks -32,-32 to -1,-1, blocks -512,0,-512 to -1,255,-1)
	Entity's Momentum: 0.00, -0.08, 0.00
Stacktrace:
	at kp.i(SourceFile:197)
	at ku.a(SourceFile:195)
	at gm.a(SourceFile:136)
	at ea.b(SourceFile:64)
	at ku.e(SourceFile:63)

-- Ticking connection --
Details:
	Connection: ku@15d9ee6
Stacktrace:
	at kx.b(SourceFile:37)
	at boc.b(SourceFile:84)
	at net.minecraft.server.MinecraftServer.u(SourceFile:483)
	at net.minecraft.server.MinecraftServer.t(SourceFile:400)
	at bnz.t(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:334)
	at jb.run(SourceFile:577)

-- System Details --
Details:
	Minecraft Version: 13w37b
	Operating System: Windows 7 (x86) version 6.1
	Java Version: 1.7.0_25, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
	Memory: 159109448 bytes (151 MB) / 518979584 bytes (494 MB) up to 518979584 bytes (494 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
	AABB Pool Size: 254 (14224 bytes; 0 MB) allocated, 254 (14224 bytes; 0 MB) used
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 99 (5544 bytes; 0 MB) allocated, 99 (5544 bytes; 0 MB) used
	Player Count: 1 / 8; [kp['CASTORgemini'/6, l='flatworld', x=-36.49, y=4.00, z=-22.53]]
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.

You can see this full report at http://hopper.minecraft.net/crashes/minecraft/MCX-145924/10723533/