[MC-29766] Crash Upon Death in Hardcore

Put the summary of the bug you're having here

Minecraft Crashed when I died in hardcore and clicked the 'delete world' option. I was prompted "are you sure?" with an button labeled 'respawn'... so I clicked it and the game crashed.

What I expected to happen was...:
I expected the world to be deleted.

What actually happened was...:
The game crashed.
Describe what happened here

Steps to Reproduce:
1. Die in a hardcore "AMPLIFIED" world
2. Click delete world
3. In confirmation dialog, click respawn.
Note: have not attempted to reproduce yet

Crash Report

---- Minecraft Crash Report ----
// Don't be sad, have a hug! <3

Time: 9/5/13 7:57 PM
Description: Ticking memory connection

java.lang.NullPointerException
	at hx.b(SourceFile:176)
	at bnf.b(SourceFile:25)
	at hx.e(SourceFile:213)
	at kl.a(SourceFile:405)
	at cx.b(SourceFile:72)
	at kl.e(SourceFile:63)
	at ko.b(SourceFile:37)
	at bnj.b(SourceFile:84)
	at net.minecraft.server.MinecraftServer.t(SourceFile:481)
	at net.minecraft.server.MinecraftServer.s(SourceFile:398)
	at bng.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:332)
	at hs.run(SourceFile:575)


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

-- Head --
Stacktrace:
	at hx.b(SourceFile:176)
	at bnf.b(SourceFile:25)
	at hx.e(SourceFile:213)
	at kl.a(SourceFile:405)
	at cx.b(SourceFile:72)
	at kl.e(SourceFile:63)

-- Ticking connection --
Details:
	Connection: kl@39ca2536
Stacktrace:
	at ko.b(SourceFile:37)
	at bnj.b(SourceFile:84)
	at net.minecraft.server.MinecraftServer.t(SourceFile:481)
	at net.minecraft.server.MinecraftServer.s(SourceFile:398)
	at bng.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:332)
	at hs.run(SourceFile:575)

-- System Details --
Details:
	Minecraft Version: 13w36a
	Operating System: Mac OS X (x86_64) version 10.7.5
	Java Version: 1.6.0_51, Apple Inc.
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Apple Inc.
	Memory: 778141216 bytes (742 MB) / 972472320 bytes (927 MB) up to 1065025536 bytes (1015 MB)
	JVM Flags: 1 total; -Xmx1G
	AABB Pool Size: 7360 (412160 bytes; 0 MB) allocated, 7075 (396200 bytes; 0 MB) used
	Suspicious classes: [com.ibm.icu.text.ArabicShapingException], [gnu.trove.TIntCollection], [gnu.trove.impl.HashFunctions, PrimeFinder], [gnu.trove.impl.hash.THash, TPrimitiveHash, TIntIntHash], [gnu.trove.iterator.TIterator, TAdvancingIterator, TIntIntIterator], [gnu.trove.map.TIntIntMap], [gnu.trove.map.hash.TIntIntHashMap], [gnu.trove.procedure.TIntIntProcedure], [gnu.trove.set.TIntSet]
	IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 3413 (191128 bytes; 0 MB) allocated, 3319 (185864 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