Hopper: java.lang.NullPointerException

This is an automatically generated report based from the following crash: http://hopper.minecraft.net/crashes/minecraft/MCX-293227/

Crash:

java.lang.NullPointerException
	at bkv.a(SourceFile:303)

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: 10/10/13 16:49
Description: Unexpected error

java.lang.NullPointerException
	at bkv.a(SourceFile:303)
	at ays.o(SourceFile:1278)
	at ays.ab(SourceFile:755)
	at ays.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 bkv.a(SourceFile:303)

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [bip['peyo56'/238, l='MpServer', x=181,93, y=80,86, z=189,65]]
	Chunk stats: MultiplayerChunkCache: 35, 35
	Level seed: 0
	Level generator: ID 00 - default, ver 1. Features enabled: false
	Level generator options: 
	Level spawn location: World: (252,64,88), Chunk: (at 12,4,8 in 15,5; contains blocks 240,0,80 to 255,255,95), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
	Level time: 62885 game time, 62885 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: 32 total; [wf['Creeper'/137, l='MpServer', x=207,50, y=11,00, z=198,50], uk['Bat'/136, l='MpServer', x=201,27, y=45,17, z=178,17], wf['Creeper'/138, l='MpServer', x=202,50, y=23,00, z=226,50], ww['Zombie'/129, l='MpServer', x=200,50, y=44,00, z=166,50], wt['Spider'/76, l='MpServer', x=150,50, y=64,00, z=156,25], ww['Zombie'/131, l='MpServer', x=201,50, y=44,00, z=166,50], ww['Zombie'/130, l='MpServer', x=200,50, y=44,00, z=167,50], uk['Bat'/133, l='MpServer', x=201,55, y=47,36, z=174,20], wt['Spider'/132, l='MpServer', x=197,44, y=44,00, z=166,28], wf['Creeper'/135, l='MpServer', x=198,50, y=45,00, z=179,50], uk['Bat'/134, l='MpServer', x=191,51, y=46,23, z=173,51], uy['Squid'/154, l='MpServer', x=239,03, y=61,34, z=146,50], uy['Squid'/155, l='MpServer', x=235,50, y=58,06, z=152,22], uy['Squid'/156, l='MpServer', x=235,22, y=60,38, z=144,72], ww['Zombie'/157, l='MpServer', x=228,50, y=16,00, z=171,50], wf['Creeper'/158, l='MpServer', x=232,50, y=16,00, z=172,50], wf['Creeper'/159, l='MpServer', x=229,50, y=16,00, z=171,50], wf['Creeper'/100, l='MpServer', x=165,50, y=17,00, z=170,97], uk['Bat'/101, l='MpServer', x=171,34, y=22,06, z=201,45], wr['Skeleton'/163, l='MpServer', x=234,25, y=64,00, z=195,75], uk['Bat'/162, l='MpServer', x=231,22, y=18,91, z=191,75], wr['Skeleton'/161, l='MpServer', x=231,50, y=64,00, z=189,50], wf['Creeper'/160, l='MpServer', x=231,50, y=16,00, z=174,50], wr['Skeleton'/166, l='MpServer', x=238,50, y=32,00, z=226,50], wr['Skeleton'/165, l='MpServer', x=235,50, y=17,00, z=237,50], wr['Skeleton'/164, l='MpServer', x=225,88, y=64,00, z=195,47], uk['Bat'/116, l='MpServer', x=193,75, y=20,89, z=232,43], uk['Bat'/291, l='MpServer', x=223,53, y=30,07, z=144,08], xm['Fireball'/115, l='MpServer', x=186,50, y=78,00, z=199,81], wf['Creeper'/114, l='MpServer', x=188,00, y=64,00, z=182,47], wr['Skeleton'/113, l='MpServer', x=187,53, y=65,00, z=148,00], bip['peyo56'/238, l='MpServer', x=181,93, y=80,86, z=189,65]]
	Retry entities: 0 total; []
	Server brand: vanilla
	Server type: Integrated singleplayer server
Stacktrace:
	at bik.a(SourceFile:302)
	at ays.b(SourceFile:1924)
	at ays.e(SourceFile:720)
	at net.minecraft.client.main.Main.main(SourceFile:103)

-- System Details --
Details:
	Minecraft Version: 13w41a
	Operating System: Linux (i386) version 3.8.0-26-generic
	Java Version: 1.7.0_21, Oracle Corporation
	Java VM Version: OpenJDK Server VM (mixed mode), Oracle Corporation
	Memory: 91380144 bytes (87 MB) / 256704512 bytes (244 MB) up to 477233152 bytes (455 MB)
	JVM Flags: 1 total; -Xmx512M
	AABB Pool Size: 6115 (342440 bytes; 0 MB) allocated, 773 (43288 bytes; 0 MB) used
	IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
	Launched Version: 13w41a
	LWJGL: 2.9.0
	OpenGL: GeForce 8200M G/integrated/SSE2/3DNOW! GL version 3.3.0 NVIDIA 310.44, NVIDIA Corporation
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Packs: [AD14:0006, AD14:0003, AD03:0000, AD02:0003, AD13:0000, AD12:0002, AD10:0000, AD00:0002, AD13:0004, AD14:0000, AD02:0000, AD02:0001, AD12:0000]
	Current Language: English (US)
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 548 (30688 bytes; 0 MB) allocated, 548 (30688 bytes; 0 MB) used

You can see this full report at http://hopper.minecraft.net/crashes/minecraft/MCX-293227/16535369/