Hopper: java.lang.NullPointerException

This is an automatically generated report based from the following crash: http://hopper.minecraft.net/crashes/minecraft/MCX-72804/

Crash:

java.lang.NullPointerException
	at ann.f(SourceFile:197)
	at hx.m(SourceFile:682)
	at net.minecraft.server.MinecraftServer.a(SourceFile:866)
	at bng.a(SourceFile:198)
	at nk.b(SourceFile:94)
	at net.minecraft.server.MinecraftServer.s(SourceFile:426)
	at bng.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:332)
	at hs.run(SourceFile:575)

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

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

Time: 9/5/13 6:21 PM
Description: Exception in server tick loop

java.lang.NullPointerException
	at ann.f(SourceFile:197)
	at hx.m(SourceFile:682)
	at net.minecraft.server.MinecraftServer.a(SourceFile:866)
	at bng.a(SourceFile:198)
	at nk.b(SourceFile:94)
	at net.minecraft.server.MinecraftServer.s(SourceFile:426)
	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:
---------------------------------------------------------------------------------------

-- System Details --
Details:
	Minecraft Version: 13w36a
	Operating System: Windows 7 (x86) version 6.1
	Java Version: 1.7.0_21, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
	Memory: 207596904 bytes (197 MB) / 454537216 bytes (433 MB) up to 518979584 bytes (494 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
	AABB Pool Size: 19817 (1109752 bytes; 1 MB) allocated, 495 (27720 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: 6321 (353976 bytes; 0 MB) allocated, 85 (4760 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-72804/8199655/