Crash After Dying in Nether Portal

Put the summary of the bug you're having here

What I expected to happen was...:
I should have respawned.

What actually happened was...:
I just stood there and didn't respawn. When I went to the title screen and tried to open my game, Minecraft crashed.

Steps to Reproduce:
1. Die while in a Nether portal.

---- Minecraft Crash Report ----
// My bad.

Time: 11/11/13 4:22 PM
Description: Ticking entity

java.lang.NullPointerException: Ticking entity
	at net.minecraft.server.MinecraftServer.a(SourceFile:635)
	at qn.b(SourceFile:1528)
	at vw.b(SourceFile:231)
	at qn.C(SourceFile:331)
	at qn.h(SourceFile:294)
	at vw.h(SourceFile:74)
	at afn.a(SourceFile:1368)
	at mj.a(SourceFile:480)
	at afn.g(SourceFile:1346)
	at afn.h(SourceFile:1253)
	at mj.h(SourceFile:365)
	at net.minecraft.server.MinecraftServer.u(SourceFile:511)
	at net.minecraft.server.MinecraftServer.t(SourceFile:441)
	at bsk.t(SourceFile:117)
	at net.minecraft.server.MinecraftServer.run(SourceFile:358)
	at ky.run(SourceFile:617)


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

-- Head --
Stacktrace:
	at net.minecraft.server.MinecraftServer.a(SourceFile:635)
	at qn.b(SourceFile:1528)
	at vw.b(SourceFile:231)
	at qn.C(SourceFile:331)
	at qn.h(SourceFile:294)
	at vw.h(SourceFile:74)
	at afn.a(SourceFile:1368)
	at mj.a(SourceFile:480)
	at afn.g(SourceFile:1346)

-- Entity being ticked --
Details:
	Entity Type: Item (vw)
	Entity ID: 14293
	Entity Name: item.tile.hellrock
	Entity's Exact location: -15.07, 67.48, 2.63
	Entity's Block location: World: (-16,67,2), Chunk: (at 0,4,2 in -1,0; contains blocks -16,0,0 to -1,255,15), Region: (-1,0; contains chunks -32,0 to -1,31, blocks -512,0,0 to -1,255,511)
	Entity's Momentum: 0.14, 0.16, 0.21
Stacktrace:
	at afn.h(SourceFile:1253)
	at mj.h(SourceFile:365)

-- Affected level --
Details:
	Level name: ---To Slay a Dragon---
	All players: 1 total; [mm['Sharpe103'/248, l='---To Slay a Dragon---', x=-15.23, y=66.00, z=2.39]]
	Chunk stats: ServerChunkCache: 474 Drop: 0
	Level seed: -4830035206600586193
	Level generator: ID 00 - default, ver 1. Features enabled: false
	Level generator options: 
	Level spawn location: World: (0,0,0), Chunk: (at 0,0,0 in 0,0; contains blocks 0,0,0 to 15,255,15), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
	Level time: 0 game time, 0 day time
	Level dimension: 0
	Level storage version: 0x00000 - Unknown?
	Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
	Level game mode: ~~ERROR~~ NullPointerException: null
Stacktrace:
	at net.minecraft.server.MinecraftServer.u(SourceFile:511)
	at net.minecraft.server.MinecraftServer.t(SourceFile:441)
	at bsk.t(SourceFile:117)
	at net.minecraft.server.MinecraftServer.run(SourceFile:358)
	at ky.run(SourceFile:617)

-- System Details --
Details:
	Minecraft Version: 1.7.2
	Operating System: Windows 7 (amd64) version 6.1
	Java Version: 1.7.0_45, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 296195544 bytes (282 MB) / 467664896 bytes (446 MB) up to 954728448 bytes (910 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
	AABB Pool Size: 1675 (93800 bytes; 0 MB) allocated, 1527 (85512 bytes; 0 MB) used
	IntCache: cache: 1, tcache: 1, allocated: 12, tallocated: 94
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 9 (504 bytes; 0 MB) allocated, 9 (504 bytes; 0 MB) used
	Player Count: 1 / 8; [mm['Sharpe103'/248, l='---To Slay a Dragon---', x=-15.23, y=66.00, z=2.39]]
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.