Hopper: java.lang.NullPointerException 1.6 cl.b(SourceFile:116)

This is an automatically generated report based from the following crash: http://hopper.minecraft.net/crashes/minecraft/MCX-46566/

Crash:

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

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

---- Minecraft Crash Report ----
// Ooh. Shiny.

Time: 10/08/13 20:18
Description: Sending packet

java.lang.NullPointerException
	at cl.b(SourceFile:116)
	at cl.a(SourceFile:41)
	at jw.b(SourceFile:436)
	at hj.b(SourceFile:644)
	at hj.a(SourceFile:79)
	at bkp.b(SourceFile:73)
	at net.minecraft.server.MinecraftServer.t(SourceFile:488)
	at net.minecraft.server.MinecraftServer.s(SourceFile:405)
	at bkm.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:339)
	at he.run(SourceFile:582)


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

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

-- Packet being sent --
Details:
	Packet ID: 4
	Packet class: fv
Stacktrace:
	at jw.b(SourceFile:436)
	at hj.b(SourceFile:644)
	at hj.a(SourceFile:79)
	at bkp.b(SourceFile:73)
	at net.minecraft.server.MinecraftServer.t(SourceFile:488)
	at net.minecraft.server.MinecraftServer.s(SourceFile:405)
	at bkm.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:339)
	at he.run(SourceFile:582)

-- System Details --
Details:
	Minecraft Version: 1.6
	Operating System: Windows Vista (x86) version 6.1
	Java Version: 1.6.0, Sun Microsystems Inc.
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Sun Microsystems Inc.
	Memory: 51304352 bytes (48 MB) / 118468608 bytes (112 MB) up to 1065484288 bytes (1016 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
	AABB Pool Size: 2994 (167664 bytes; 0 MB) allocated, 2994 (167664 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: 6320 (353920 bytes; 0 MB) allocated, 6316 (353696 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-46566/1996974/