Hopper: java.lang.NullPointerException

java.lang.NullPointerException
	at ik.a(SourceFile:584)
	at ik.a(SourceFile:537)
	at aa.b(SourceFile:124)
	at net.minecraft.server.MinecraftServer.a(SourceFile:706)
	at ka.a(SourceFile:767)
	at dl.a(SourceFile:33)
	at cn.b(SourceFile:64)
	at ka.e(SourceFile:60)

---- Minecraft Crash Report ----
// You're mean.

Time: 9/19/13 7:21 PM
Description: Ticking memory connection

java.lang.NullPointerException
	at ik.a(SourceFile:584)
	at ik.a(SourceFile:537)
	at aa.b(SourceFile:124)
	at net.minecraft.server.MinecraftServer.a(SourceFile:706)
	at ka.a(SourceFile:767)
	at dl.a(SourceFile:33)
	at cn.b(SourceFile:64)
	at ka.e(SourceFile:60)
	at kd.b(SourceFile:37)
	at blc.b(SourceFile:84)
	at net.minecraft.server.MinecraftServer.t(SourceFile:489)
	at net.minecraft.server.MinecraftServer.s(SourceFile:406)
	at bkz.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:340)
	at hi.run(SourceFile:583)


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

-- Head --
Stacktrace:
	at ik.a(SourceFile:584)
	at ik.a(SourceFile:537)
	at aa.b(SourceFile:124)
	at net.minecraft.server.MinecraftServer.a(SourceFile:706)
	at ka.a(SourceFile:767)
	at dl.a(SourceFile:33)
	at cn.b(SourceFile:64)
	at ka.e(SourceFile:60)

-- Ticking connection --
Details:
	Connection: ka@432417
Stacktrace:
	at kd.b(SourceFile:37)
	at blc.b(SourceFile:84)
	at net.minecraft.server.MinecraftServer.t(SourceFile:489)
	at net.minecraft.server.MinecraftServer.s(SourceFile:406)
	at bkz.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:340)
	at hi.run(SourceFile:583)

-- System Details --
Details:
	Minecraft Version: 1.6.4
	Operating System: Windows 7 (x86) version 6.1
	Java Version: 1.7.0_25, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
	Memory: 109807720 bytes (104 MB) / 223059968 bytes (212 MB) up to 518979584 bytes (494 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
	AABB Pool Size: 4275 (239400 bytes; 0 MB) allocated, 3866 (216496 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 15, tcache: 0, allocated: 3, tallocated: 63
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 1444 (80864 bytes; 0 MB) allocated, 1249 (69944 bytes; 0 MB) used
	Player Count: 1 / 8; [jv['willy75726'/323, l='SERVER', x=150.72, y=64.00, z=262.14]]
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.