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-42398/

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 awv.a(SourceFile:168)
	at axm.a(SourceFile:31)
	at axs.a(SourceFile:49)

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

---- Minecraft Crash Report ----
// I just don't know what went wrong :(

Time: 07/08/13 18:37
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 awv.a(SourceFile:168)
	at axm.a(SourceFile:31)
	at axs.a(SourceFile:49)
	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 awv.a(SourceFile:168)
	at axm.a(SourceFile:31)
	at axs.a(SourceFile:49)

-- Screen render details --
Details:
	Screen name: axs
	Mouse location: Scaled: (308, 168). Absolute: (616, 321)
	Screen size: Scaled: (640, 329). Absolute: (1280, 658). Scale factor of 2

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [bdf['ethanrjones'/4898, l='MpServer', x=-79.67, y=67.62, z=253.42]]
	Chunk stats: MultiplayerChunkCache: 441
	Level seed: 0
	Level generator: ID 00 - default, ver 1. Features enabled: false
	Level generator options: 
	Level spawn location: World: (-44,64,252), Chunk: (at 4,4,12 in -3,15; contains blocks -48,0,240 to -33,255,255), Region: (-1,0; contains chunks -32,0 to -1,31, blocks -512,0,0 to -1,255,511)
	Level time: 60853 game time, 60853 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: survival (ID 0). Hardcore: false. Cheats: false
	Forced entities: 55 total; [ry['Sheep'/4765, l='MpServer', x=-159.78, y=66.00, z=236.19], rn['Bat'/4870, l='MpServer', x=-9.26, y=51.66, z=333.14], rx['Pig'/4764, l='MpServer', x=-160.06, y=66.00, z=239.97], rx['Pig'/4766, l='MpServer', x=-151.06, y=65.00, z=263.09], ry['Sheep'/4868, l='MpServer', x=-7.47, y=67.00, z=316.19], ry['Sheep'/4866, l='MpServer', x=-12.44, y=68.00, z=308.25], ry['Sheep'/4865, l='MpServer', x=-8.66, y=66.00, z=294.44], ry['Sheep'/4864, l='MpServer', x=-15.66, y=68.00, z=218.78], rn['Bat'/4778, l='MpServer', x=-133.25, y=39.10, z=293.75], rq['Cow'/4776, l='MpServer', x=-137.16, y=67.00, z=219.88], rq['Cow'/4777, l='MpServer', x=-140.97, y=67.00, z=225.94], st['entity.MinecartChest.name'/4774, l='MpServer', x=-131.50, y=43.50, z=180.50], rq['Cow'/4775, l='MpServer', x=-134.41, y=69.00, z=194.50], rn['Bat'/6528, l='MpServer', x=-140.43, y=24.79, z=184.39], rq['Cow'/4798, l='MpServer', x=-96.13, y=65.00, z=181.91], rq['Cow'/4794, l='MpServer', x=-105.31, y=66.00, z=292.53], bdf['ethanrjones'/4898, l='MpServer', x=-79.67, y=67.62, z=253.42], rq['Cow'/4793, l='MpServer', x=-128.84, y=67.00, z=222.91], rq['Cow'/4792, l='MpServer', x=-121.53, y=67.00, z=233.03], ry['Sheep'/4811, l='MpServer', x=-82.84, y=64.00, z=185.06], rn['Bat'/4812, l='MpServer', x=-80.22, y=55.10, z=247.69], rn['Bat'/4813, l='MpServer', x=-89.25, y=56.10, z=251.34], rn['Bat'/4814, l='MpServer', x=-89.25, y=55.10, z=253.75], rn['Bat'/4815, l='MpServer', x=-93.72, y=50.00, z=234.64], rn['Bat'/4800, l='MpServer', x=-97.38, y=50.10, z=273.75], rn['Bat'/4801, l='MpServer', x=-106.15, y=54.00, z=304.80], ry['Sheep'/4825, l='MpServer', x=-73.22, y=63.00, z=173.56], ry['Sheep'/4824, l='MpServer', x=-66.34, y=67.00, z=174.50], ua['Villager'/4827, l='MpServer', x=-79.50, y=66.00, z=255.50], ry['Sheep'/4826, l='MpServer', x=-68.63, y=68.00, z=206.53], rq['Cow'/4829, l='MpServer', x=-72.34, y=67.00, z=312.53], ua['Villager'/4828, l='MpServer', x=-79.50, y=66.00, z=257.31], rn['Bat'/4831, l='MpServer', x=-62.25, y=53.10, z=267.25], rn['Bat'/6524, l='MpServer', x=-56.82, y=13.84, z=311.04], rn['Bat'/4817, l='MpServer', x=-89.13, y=50.10, z=272.50], rn['Bat'/4816, l='MpServer', x=-90.25, y=50.10, z=271.25], ry['Sheep'/4842, l='MpServer', x=-38.09, y=69.00, z=198.94], rq['Cow'/4843, l='MpServer', x=-36.25, y=68.00, z=250.22], ry['Sheep'/4840, l='MpServer', x=-42.03, y=69.00, z=197.03], ry['Sheep'/4841, l='MpServer', x=-36.28, y=69.00, z=187.63], ry['Sheep'/4844, l='MpServer', x=-42.88, y=70.00, z=302.09], ry['Sheep'/4845, l='MpServer', x=-34.50, y=78.00, z=311.50], rn['Bat'/4834, l='MpServer', x=-62.50, y=52.10, z=270.03], rn['Bat'/4835, l='MpServer', x=-54.75, y=53.10, z=264.25], rn['Bat'/4832, l='MpServer', x=-55.44, y=56.10, z=266.25], rn['Bat'/4833, l='MpServer', x=-55.75, y=53.10, z=261.75], rq['Cow'/4836, l='MpServer', x=-49.63, y=69.00, z=264.63], rq['Cow'/4837, l='MpServer', x=-55.88, y=73.00, z=316.03], rq['Cow'/4859, l='MpServer', x=-25.84, y=68.00, z=236.13], ry['Sheep'/4858, l='MpServer', x=-19.94, y=69.00, z=224.13], ry['Sheep'/4857, l='MpServer', x=-28.50, y=77.00, z=218.50], ry['Sheep'/4856, l='MpServer', x=-29.13, y=70.00, z=193.06], ry['Sheep'/4861, l='MpServer', x=-12.50, y=70.00, z=311.66], rq['Cow'/4860, l='MpServer', x=-24.38, y=68.00, z=233.19], ry['Sheep'/4855, l='MpServer', x=-17.03, y=69.00, z=199.03]]
	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 (amd64) version 6.1
	Java Version: 1.7.0_11, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 157012592 bytes (149 MB) / 462356480 bytes (440 MB) up to 954466304 bytes (910 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
	AABB Pool Size: 6470 (362320 bytes; 0 MB) allocated, 1833 (102648 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 3, tallocated: 63
	Launched Version: 1.6.2
	LWJGL: 2.9.0
	OpenGL: ATI Radeon HD 5400 Series GL version 4.2.12002 Compatibility Profile Context 9.12.0.0, ATI Technologies Inc.
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Pack: Sphax PureBDcraft 128x MC16-converted-1375464035455.zip
	Current Language: English (US)
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 1303 (72968 bytes; 0 MB) allocated, 242 (13552 bytes; 0 MB) used

You can see this full report at http://hopper.minecraft.net/crashes/minecraft/MCX-42398/1174198/