Hopper: java.lang.NullPointerException

This is an automatically generated report based from the following crash: http://hopper.minecraft.net/crashes/minecraft/MCX-247422/

Crash:

java.lang.NullPointerException
	at zi.g(SourceFile:151)
	at zi.i(SourceFile:171)

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

---- Minecraft Crash Report ----
// Why is it breaking :(

Time: 2013-09-27 14:29
Description: Adding item to inventory

java.lang.NullPointerException
	at zi.g(SourceFile:151)
	at zi.i(SourceFile:171)
	at vd.a(SourceFile:234)
	at tq.b_(SourceFile:199)
	at vf.r(SourceFile:436)
	at vf.e(SourceFile:428)
	at pb.h(SourceFile:1194)
	at vf.h(SourceFile:211)
	at kq.i(SourceFile:204)
	at kv.a(SourceFile:201)
	at gs.a(SourceFile:136)
	at eb.b(SourceFile:63)
	at kv.e(SourceFile:69)
	at ky.b(SourceFile:40)
	at box.b(SourceFile:83)
	at net.minecraft.server.MinecraftServer.u(SourceFile:494)
	at net.minecraft.server.MinecraftServer.t(SourceFile:411)
	at bou.t(SourceFile:121)
	at net.minecraft.server.MinecraftServer.run(SourceFile:346)
	at jc.run(SourceFile:582)


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

-- Head --
Stacktrace:
	at zi.g(SourceFile:151)
	at zi.i(SourceFile:171)

-- Item being added --
Details:
	Item ID: 0
	Item data: 0
	Item name: ~~ERROR~~ NullPointerException: null
Stacktrace:
	at vd.a(SourceFile:234)
	at tq.b_(SourceFile:199)
	at vf.r(SourceFile:436)
	at vf.e(SourceFile:428)
	at pb.h(SourceFile:1194)
	at vf.h(SourceFile:211)

-- Player being ticked --
Details:
	Entity Type: null (kq)
	Entity ID: 654
	Entity Name: mr_orangutang
	Entity's Exact location: 733,76, 75,55, -1968,75
	Entity's Block location: World: (733,75,-1969), Chunk: (at 13,4,15 in 45,-124; contains blocks 720,0,-1984 to 735,255,-1969), Region: (1,-4; contains chunks 32,-128 to 63,-97, blocks 512,0,-2048 to 1023,255,-1537)
	Entity's Momentum: 0,00, 0,00, 0,00
Stacktrace:
	at kq.i(SourceFile:204)
	at kv.a(SourceFile:201)
	at gs.a(SourceFile:136)
	at eb.b(SourceFile:63)
	at kv.e(SourceFile:69)

-- Ticking connection --
Details:
	Connection: kv@56fc15cb
Stacktrace:
	at ky.b(SourceFile:40)
	at box.b(SourceFile:83)
	at net.minecraft.server.MinecraftServer.u(SourceFile:494)
	at net.minecraft.server.MinecraftServer.t(SourceFile:411)
	at bou.t(SourceFile:121)
	at net.minecraft.server.MinecraftServer.run(SourceFile:346)
	at jc.run(SourceFile:582)

-- System Details --
Details:
	Minecraft Version: 13w39b
	Operating System: Mac OS X (x86_64) version 10.8.5
	Java Version: 1.6.0_51, Apple Inc.
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Apple Inc.
	Memory: 76123856 bytes (72 MB) / 251076608 bytes (239 MB) up to 1065025536 bytes (1015 MB)
	JVM Flags: 1 total; -Xmx1G
	AABB Pool Size: 5636 (315616 bytes; 0 MB) allocated, 5564 (311584 bytes; 0 MB) used
	IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 1558 (87248 bytes; 0 MB) allocated, 1446 (80976 bytes; 0 MB) used
	Player Count: 1 / 8; [kq['mr_orangutang'/654, l='MEDLY', x=733,76, y=75,55, z=-1968,75]]
	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-247422/14581179/