Multiplayer, crash

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

Time: 1/13/13 11:15 AM
Description: Exception in world tick

java.lang.NullPointerException
	at ayh.a(SourceFile:452)
	at dj.a(SourceFile:27)
	at cg.b(SourceFile:349)
	at ayh.d(SourceFile:80)
	at ayp.b(SourceFile:57)
	at net.minecraft.client.Minecraft.l(SourceFile:1332)
	at net.minecraft.client.Minecraft.J(SourceFile:582)
	at net.minecraft.client.Minecraft.run(SourceFile:534)
	at java.lang.Thread.run(Unknown Source)


A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- Head --
Stacktrace:
	at ayh.a(SourceFile:452)
	at dj.a(SourceFile:27)
	at cg.b(SourceFile:349)
	at ayh.d(SourceFile:80)
	at ayp.b(SourceFile:57)

-- Affected level --
Details:
	Problem: Level is null!
Stacktrace:
	at net.minecraft.client.Minecraft.l(SourceFile:1332)
	at net.minecraft.client.Minecraft.J(SourceFile:582)
	at net.minecraft.client.Minecraft.run(SourceFile:534)
	at java.lang.Thread.run(Unknown Source)

-- System Details --
Details:
	Minecraft Version: 1.4.7
	Operating System: Windows 7 (x86) version 6.1
	Java Version: 1.7.0_09, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Oracle Corporation
	Memory: 465437112 bytes (443 MB) / 519110656 bytes (495 MB) up to 1037959168 bytes (989 MB)
	JVM Flags: 2 total; -Xms512m -Xmx1024m
	AABB Pool Size: 50 (2800 bytes; 0 MB) allocated, 15 (840 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 3, tallocated: 63
	LWJGL: 2.4.2
	OpenGL: GeForce 6150SE nForce 430/PCI/SSE2 GL version 2.1.2, NVIDIA Corporation
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Texture Pack: Default
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: ~~ERROR~~ NullPointerException: null