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-7483/

Crash:

java.lang.IllegalArgumentException: Modifier name cannot be empty
	at org.apache.commons.lang3.Validate.notEmpty(Validate.java:398)
	at os.<init>(SourceFile:31)
	at to.a(SourceFile:94)
	at yd.D(SourceFile:580)
	at yd.a(SourceFile:471)
	at awv.a(SourceFile:188)
	at axj.a(SourceFile:580)
	at awv.a(SourceFile:168)
	at axm.a(SourceFile:31)
	at axj.a(SourceFile:529)

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

---- Minecraft Crash Report ----
// You're mean.

Time: 02/08/13 20:43
Description: Rendering screen

java.lang.IllegalArgumentException: Modifier name cannot be empty
	at org.apache.commons.lang3.Validate.notEmpty(Validate.java:398)
	at os.<init>(SourceFile:31)
	at to.a(SourceFile:94)
	at yd.D(SourceFile:580)
	at yd.a(SourceFile:471)
	at awv.a(SourceFile:188)
	at axj.a(SourceFile:580)
	at awv.a(SourceFile:168)
	at axm.a(SourceFile:31)
	at axj.a(SourceFile:529)
	at bfb.b(SourceFile:718)
	at ats.S(SourceFile:686)
	at ats.d(SourceFile:619)
	at net.minecraft.client.main.Main.main(SourceFile:101)


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 os.<init>(SourceFile:31)
	at to.a(SourceFile:94)
	at yd.D(SourceFile:580)
	at yd.a(SourceFile:471)
	at awv.a(SourceFile:188)
	at axj.a(SourceFile:580)
	at awv.a(SourceFile:168)
	at axm.a(SourceFile:31)
	at axj.a(SourceFile:529)

-- Screen render details --
Details:
	Screen name: axj
	Mouse location: Scaled: (386, 226). Absolute: (772, 253)
	Screen size: Scaled: (683, 353). Absolute: (1366, 706). Scale factor of 2

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [bdf['ConnorTHD'/0, l='MpServer', x=-765.99, y=6.62, z=1694.61]]
	Chunk stats: MultiplayerChunkCache: 441
	Level seed: 0
	Level generator: ID 01 - flat, ver 0. Features enabled: false
	Level generator options: 
	Level spawn location: World: (-759,4,1675), Chunk: (at 9,0,11 in -48,104; contains blocks -768,0,1664 to -753,255,1679), Region: (-2,3; contains chunks -64,96 to -33,127, blocks -1024,0,1536 to -513,255,2047)
	Level time: 46886 game time, 46886 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: 1 total; [bdf['ConnorTHD'/0, l='MpServer', x=-765.99, y=6.62, z=1694.61]]
	Retry entities: 0 total; []
	Server brand: vanilla
	Server type: Integrated singleplayer server
Stacktrace:
	at bda.a(SourceFile:284)
	at ats.b(SourceFile:1761)
	at ats.d(SourceFile:628)
	at net.minecraft.client.main.Main.main(SourceFile:101)

-- System Details --
Details:
	Minecraft Version: 1.6.2
	Operating System: Windows 7 (x86) version 6.1
	Java Version: 1.6.0_31, Sun Microsystems Inc.
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Sun Microsystems Inc.
	Memory: 161091504 bytes (153 MB) / 290639872 bytes (277 MB) up to 1037959168 bytes (989 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
	AABB Pool Size: 3254 (182224 bytes; 0 MB) allocated, 17 (952 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	Launched Version: 1.6.2
	LWJGL: 2.9.0
	OpenGL: ATI Mobility Radeon HD 4200 Series GL version 3.3.11672 Compatibility Profile Context, ATI Technologies Inc.
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Pack: Default
	Current Language: English (US)
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 43 (2408 bytes; 0 MB) allocated, 43 (2408 bytes; 0 MB) used

You can see this full report at http://hopper.minecraft.net/crashes/minecraft/MCX-7483/96226/