Hopper: java.lang.NullPointerException

java.lang.NullPointerException
	at avc.a(SourceFile:51)
	at awe.a(SourceFile:69)
	at awe.d(SourceFile:128)
	at awe.m(SourceFile:107)

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

Time: 19/09/13 17:44
Description: Updating screen events

java.lang.NullPointerException
	at avc.a(SourceFile:51)
	at awe.a(SourceFile:69)
	at awe.d(SourceFile:128)
	at awe.m(SourceFile:107)
	at atv.k(SourceFile:1158)
	at atv.S(SourceFile:663)
	at atv.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 avc.a(SourceFile:51)
	at awe.a(SourceFile:69)
	at awe.d(SourceFile:128)
	at awe.m(SourceFile:107)

-- Affected screen --
Details:
	Screen name: blt
Stacktrace:
	at atv.k(SourceFile:1158)
	at atv.S(SourceFile:663)
	at atv.d(SourceFile:619)
	at net.minecraft.client.main.Main.main(SourceFile:101)

-- System Details --
Details:
	Minecraft Version: 1.6.4
	Operating System: Windows XP (x86) version 5.1
	Java Version: 1.7.0_25, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
	Memory: 341150160 bytes (325 MB) / 458670080 bytes (437 MB) up to 518979584 bytes (494 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
	AABB Pool Size: 22791 (1276296 bytes; 1 MB) allocated, 2 (112 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 3, tallocated: 63
	Launched Version: 1.6.4
	LWJGL: 2.9.0
	OpenGL: Intel 945GM GL version 1.4.0 - Build 7.14.10.4926, Intel
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Pack: Default
	Current Language: English (UK)
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: ~~ERROR~~ NullPointerException: null