Hopper: java.lang.NullPointerException

This is an automatically generated report based from the following crash: http://hopper.minecraft.net/crashes/minecraft/MCX-296685/

Crash:

java.lang.NullPointerException
	at cm.b(SourceFile:116)
	at cm.a(SourceFile:41)

The following is the first clean report made public about this crash:

---- Minecraft Crash Report ----
// Don't be sad. I'll do better next time, I promise!

Time: 10/10/13 15:57
Description: Sending packet

java.lang.NullPointerException
	at cm.b(SourceFile:116)
	at cm.a(SourceFile:41)
	at jx.b(SourceFile:436)
	at hk.b(SourceFile:644)
	at hk.a(SourceFile:79)
	at bkr.b(SourceFile:73)
	at net.minecraft.server.MinecraftServer.t(SourceFile:488)
	at net.minecraft.server.MinecraftServer.s(SourceFile:405)
	at bko.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:339)
	at hf.run(SourceFile:582)


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

-- Head --
Stacktrace:
	at cm.b(SourceFile:116)
	at cm.a(SourceFile:41)

-- Packet being sent --
Details:
	Packet ID: 4
	Packet class: fw
Stacktrace:
	at jx.b(SourceFile:436)
	at hk.b(SourceFile:644)
	at hk.a(SourceFile:79)
	at bkr.b(SourceFile:73)
	at net.minecraft.server.MinecraftServer.t(SourceFile:488)
	at net.minecraft.server.MinecraftServer.s(SourceFile:405)
	at bko.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:339)
	at hf.run(SourceFile:582)

-- System Details --
Details:
	Minecraft Version: 1.6.1
	Operating System: Windows 8 (x86) version 6.2
	Java Version: 1.7.0_40, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
	Memory: 95528264 bytes (91 MB) / 161447936 bytes (153 MB) up to 518979584 bytes (494 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
	AABB Pool Size: 1597 (89432 bytes; 0 MB) allocated, 1597 (89432 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 1, tallocated: 63
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 347 (19432 bytes; 0 MB) allocated, 347 (19432 bytes; 0 MB) used
	Player Count: 0 / 8; []
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.

You can see this full report at http://hopper.minecraft.net/crashes/minecraft/MCX-296685/16618665/