Hopper: java.lang.NullPointerException

java.lang.NullPointerException
	at uf.<init>(SourceFile:99)
	at beu.<init>(SourceFile:26)
	at bey.<init>(SourceFile:21)
	at bcw.a(SourceFile:300)
	at di.a(SourceFile:68)
	at co.b(SourceFile:354)
	at bcw.e(SourceFile:98)
	at bdd.b(SourceFile:60)

---- Minecraft Crash Report ----
// Why is it breaking :(

Time: 15/10/13 9:14 PM
Description: Exception in world tick

java.lang.NullPointerException
	at uf.<init>(SourceFile:99)
	at beu.<init>(SourceFile:26)
	at bey.<init>(SourceFile:21)
	at bcw.a(SourceFile:300)
	at di.a(SourceFile:68)
	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 uf.<init>(SourceFile:99)
	at beu.<init>(SourceFile:26)
	at bey.<init>(SourceFile:21)
	at bcw.a(SourceFile:300)
	at di.a(SourceFile:68)
	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: Windows Vista (x86) version 6.0
	Java Version: 1.7.0_25, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
	Memory: 57848144 bytes (55 MB) / 100777984 bytes (96 MB) up to 518979584 bytes (494 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
	AABB Pool Size: 18931 (1060136 bytes; 1 MB) allocated, 16 (896 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: GeForce 9500 GS/PCIe/SSE2 GL version 3.3.0, NVIDIA Corporation
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Pack: Default
	Current Language: English (US)
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: ~~ERROR~~ NullPointerException: null