Hopper: java.lang.NullPointerException

java.lang.NullPointerException
	at bcw.a(SourceFile:651)
	at bcw.a(SourceFile:344)
	at eq.a(SourceFile:150)
	at co.b(SourceFile:354)
	at bcw.e(SourceFile:98)
	at bdd.b(SourceFile:60)

---- Minecraft Crash Report ----
// Daisy, daisy...

Time: 9/21/13 8:39 PM
Description: Exception in world tick

java.lang.NullPointerException
	at bcw.a(SourceFile:651)
	at bcw.a(SourceFile:344)
	at eq.a(SourceFile:150)
	at co.b(SourceFile:354)
	at bcw.e(SourceFile:98)
	at bdd.b(SourceFile:60)
	at atv.k(SourceFile:1386)
	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 bcw.a(SourceFile:651)
	at bcw.a(SourceFile:344)
	at eq.a(SourceFile:150)
	at co.b(SourceFile:354)
	at bcw.e(SourceFile:98)
	at bdd.b(SourceFile:60)

-- Affected level --
Details:
	Problem: Level is null!
Stacktrace:
	at atv.k(SourceFile:1386)
	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: Mac OS X (x86_64) version 10.8.5
	Java Version: 1.6.0_51, Apple Inc.
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Apple Inc.
	Memory: 154246648 bytes (147 MB) / 204234752 bytes (194 MB) up to 1060372480 bytes (1011 MB)
	JVM Flags: 1 total; -Xmx1G
	AABB Pool Size: 960 (53760 bytes; 0 MB) allocated, 266 (14896 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: NVIDIA GeForce GT 650M OpenGL Engine GL version 2.1 NVIDIA-8.16.74 310.40.00.10f02, NVIDIA Corporation
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Pack: oCd pack 1
	Current Language: English (US)
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: ~~ERROR~~ NullPointerException: null