Hopper: java.lang.NullPointerException

This is an automatically generated report based from the following crash: http://hopper.minecraft.net/crashes/minecraft/MCX-196502/

Crash:

java.lang.NullPointerException
	at afm.a(SourceFile:57)
	at afk.a(SourceFile:423)
	at ade.d(SourceFile:309)
	at ade.b(SourceFile:400)
	at ask.a(SourceFile:120)

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

---- Minecraft Crash Report ----
// Don't be sad. I'll do better next time, I promise!

Time: 9/20/13 10:03 AM
Description: Exception while updating neighbours

java.lang.NullPointerException
	at afm.a(SourceFile:57)
	at afk.a(SourceFile:423)
	at ade.d(SourceFile:309)
	at ade.b(SourceFile:400)
	at ask.a(SourceFile:120)
	at ade.e(SourceFile:462)
	at ade.d(SourceFile:442)
	at ade.c(SourceFile:410)
	at ade.d(SourceFile:319)
	at ade.f(SourceFile:372)
	at kr.d(SourceFile:173)
	at kr.b(SourceFile:198)
	at kr.a(SourceFile:110)
	at kv.a(SourceFile:326)
	at gu.a(SourceFile:46)
	at eb.b(SourceFile:63)
	at kv.e(SourceFile:64)
	at ky.b(SourceFile:37)
	at bow.b(SourceFile:83)
	at net.minecraft.server.MinecraftServer.u(SourceFile:487)
	at net.minecraft.server.MinecraftServer.t(SourceFile:404)
	at bot.t(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:338)
	at jc.run(SourceFile:581)


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

-- Head --
Stacktrace:
	at afm.a(SourceFile:57)
	at afk.a(SourceFile:423)
	at ade.d(SourceFile:309)
	at ade.b(SourceFile:400)
	at ask.a(SourceFile:120)

-- Block being updated --
Details:
	Source block type: ID #49 (tile.obsidian // ash)
	Block type: ID #90 (tile.portal // ask)
	Block data value: 0 / 0x0 / 0b0000
	Block location: World: (102,72,45), Chunk: (at 6,4,13 in 6,2; contains blocks 96,0,32 to 111,255,47), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Stacktrace:
	at ade.e(SourceFile:462)
	at ade.d(SourceFile:442)
	at ade.c(SourceFile:410)
	at ade.d(SourceFile:319)
	at ade.f(SourceFile:372)
	at kr.d(SourceFile:173)
	at kr.b(SourceFile:198)
	at kr.a(SourceFile:110)
	at kv.a(SourceFile:326)
	at gu.a(SourceFile:46)
	at eb.b(SourceFile:63)
	at kv.e(SourceFile:64)

-- Ticking connection --
Details:
	Connection: kv@109bb90
Stacktrace:
	at ky.b(SourceFile:37)
	at bow.b(SourceFile:83)
	at net.minecraft.server.MinecraftServer.u(SourceFile:487)
	at net.minecraft.server.MinecraftServer.t(SourceFile:404)
	at bot.t(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:338)
	at jc.run(SourceFile:581)

-- System Details --
Details:
	Minecraft Version: 13w38b
	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: 113321816 bytes (108 MB) / 323354624 bytes (308 MB) up to 518979584 bytes (494 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
	AABB Pool Size: 4231 (236936 bytes; 0 MB) allocated, 3850 (215600 bytes; 0 MB) used
	IntCache: cache: 4, tcache: 85, allocated: 12, tallocated: 94
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 302 (16912 bytes; 0 MB) allocated, 299 (16744 bytes; 0 MB) used
	Player Count: 1 / 8; [kq['firefly9809'/192, l='Snapshot', x=105.91, y=71.99, z=45.35]]
	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-196502/12593780/