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-398573/

Crash:

java.lang.IllegalArgumentException: Modifier name cannot be empty
	at org.apache.commons.lang3.Validate.notEmpty(Validate.java:398)
	at rs.<init>(SourceFile:29)
	at ws.a(SourceFile:94)
	at abm.D(SourceFile:594)
	at abm.a(SourceFile:482)
	at bbw.a(SourceFile:76)
	at bcw.a(SourceFile:166)

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

---- Minecraft Crash Report ----
// Hi. I'm Minecraft, and I'm a crashaholic.

Time: 10/18/13 6:47 PM
Description: Rendering screen

java.lang.IllegalArgumentException: Modifier name cannot be empty
	at org.apache.commons.lang3.Validate.notEmpty(Validate.java:398)
	at rs.<init>(SourceFile:29)
	at ws.a(SourceFile:94)
	at abm.D(SourceFile:594)
	at abm.a(SourceFile:482)
	at bbw.a(SourceFile:76)
	at bcw.a(SourceFile:166)
	at blc.b(SourceFile:850)
	at ayw.ad(SourceFile:782)
	at ayw.e(SourceFile:706)
	at net.minecraft.client.main.Main.main(SourceFile:103)


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 rs.<init>(SourceFile:29)
	at ws.a(SourceFile:94)
	at abm.D(SourceFile:594)
	at abm.a(SourceFile:482)
	at bbw.a(SourceFile:76)
	at bcw.a(SourceFile:166)

-- Screen render details --
Details:
	Screen name: bdh
	Mouse location: Scaled: (174, 78). Absolute: (524, 560)
	Screen size: Scaled: (480, 265). Absolute: (1440, 795). Scale factor of 3

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [biw['grantwarfield'/18, l='MpServer', x=69.26, y=93.31, z=743.54]]
	Chunk stats: MultiplayerChunkCache: 225, 225
	Level seed: 0
	Level generator: ID 01 - flat, ver 0. Features enabled: false
	Level generator options: 
	Level spawn location: World: (105,4,771), Chunk: (at 9,0,3 in 6,48; contains blocks 96,0,768 to 111,255,783), Region: (0,1; contains chunks 0,32 to 31,63, blocks 0,0,512 to 511,255,1023)
	Level time: 211756 game time, 211756 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: 19 total; [vb['Squid'/0, l='MpServer', x=64.47, y=54.46, z=759.58], biw['grantwarfield'/18, l='MpServer', x=69.26, y=93.31, z=743.54], vb['Squid'/1, l='MpServer', x=64.87, y=53.00, z=760.50], un['Bat'/2, l='MpServer', x=71.78, y=56.51, z=728.88], un['Bat'/3, l='MpServer', x=69.47, y=59.92, z=735.06], un['Bat'/4, l='MpServer', x=97.06, y=58.07, z=752.63], un['Bat'/5, l='MpServer', x=105.53, y=56.48, z=749.00], un['Bat'/6, l='MpServer', x=84.16, y=58.76, z=786.63], un['Bat'/7, l='MpServer', x=85.19, y=56.01, z=775.34], un['Bat'/8, l='MpServer', x=102.28, y=57.45, z=762.91], wb['entity.MinecartRideable.name'/9, l='MpServer', x=100.50, y=59.50, z=770.47], vz['entity.MinecartFurnace.name'/10, l='MpServer', x=100.50, y=59.50, z=771.47], un['Bat'/11, l='MpServer', x=101.91, y=58.28, z=772.16], un['Bat'/12, l='MpServer', x=99.00, y=66.29, z=794.09], un['Bat'/13, l='MpServer', x=106.66, y=56.17, z=785.50], un['Bat'/14, l='MpServer', x=124.78, y=57.20, z=767.97], un['Bat'/15, l='MpServer', x=117.34, y=57.32, z=784.66], un['Bat'/16, l='MpServer', x=137.34, y=56.54, z=805.19], un['Bat'/813, l='MpServer', x=93.61, y=56.92, z=758.03]]
	Retry entities: 0 total; []
	Server brand: vanilla
	Server type: Integrated singleplayer server
Stacktrace:
	at bir.a(SourceFile:284)
	at ayw.b(SourceFile:1938)
	at ayw.e(SourceFile:715)
	at net.minecraft.client.main.Main.main(SourceFile:103)

-- System Details --
Details:
	Minecraft Version: 13w42b
	Operating System: Mac OS X (x86_64) version 10.7.5
	Java Version: 1.6.0_45, Apple Inc.
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Apple Inc.
	Memory: 89241576 bytes (85 MB) / 266072064 bytes (253 MB) up to 1069416448 bytes (1019 MB)
	JVM Flags: 1 total; -Xmx1G
	AABB Pool Size: 1574 (88144 bytes; 0 MB) allocated, 173 (9688 bytes; 0 MB) used
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	Launched Version: 13w42b
	LWJGL: 2.9.1
	OpenGL: NVIDIA GeForce 320M OpenGL Engine GL version 2.1 NVIDIA-7.32.12, NVIDIA Corporation
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Packs: []
	Current Language: English (US)
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 1263 (70728 bytes; 0 MB) allocated, 143 (8008 bytes; 0 MB) used
	Anisotropic Filtering: Off (1)

You can see this full report at http://hopper.minecraft.net/crashes/minecraft/MCX-398573/19252094/