CSP - Crash loading old world

Snapshot crashed while loading a CSP world. This crash only happened once, and I cannot seem to replicate it. Figured I'd post it here anyway.

---- Minecraft Crash Report ----
// Would you like a cupcake?

Time: 5/10/13 11:41 AM
Description: Sending packet

java.lang.NullPointerException
	at cj.b(SourceFile:116)
	at cj.a(SourceFile:41)
	at jj.b(SourceFile:426)
	at gw.b(SourceFile:668)
	at gw.a(SourceFile:78)
	at bhf.b(SourceFile:73)
	at net.minecraft.server.MinecraftServer.s(SourceFile:490)
	at net.minecraft.server.MinecraftServer.r(SourceFile:407)
	at bhc.r(SourceFile:125)
	at net.minecraft.server.MinecraftServer.run(SourceFile:341)
	at gr.run(SourceFile:584)


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

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

-- Packet being sent --
Details:
	Packet ID: 4
	Packet class: fj
Stacktrace:
	at jj.b(SourceFile:426)
	at gw.b(SourceFile:668)
	at gw.a(SourceFile:78)
	at bhf.b(SourceFile:73)
	at net.minecraft.server.MinecraftServer.s(SourceFile:490)
	at net.minecraft.server.MinecraftServer.r(SourceFile:407)
	at bhc.r(SourceFile:125)
	at net.minecraft.server.MinecraftServer.run(SourceFile:341)
	at gr.run(SourceFile:584)

-- System Details --
Details:
	Minecraft Version: 13w19a
	Operating System: Linux (amd64) version 3.5.0-17-generic
	Java Version: 1.7.0_21, Oracle Corporation
	Java VM Version: OpenJDK 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 300135048 bytes (286 MB) / 449576960 bytes (428 MB) up to 954466304 bytes (910 MB)
	JVM Flags: 1 total; -Xmx1G
	AABB Pool Size: 457 (25592 bytes; 0 MB) allocated, 443 (24808 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: 52 (2912 bytes; 0 MB) allocated, 52 (2912 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.