minecraft crashes when an item is given a negitive ammount using mcedit then given an attribute.

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

Time: 7/2/13 4:30 PM
Description: Ticking player

java.lang.IllegalArgumentException: Modifier name cannot be empty
	at org.apache.commons.lang3.Validate.notEmpty(Validate.java:398)
	at oq.<init>(SourceFile:31)
	at tm.a(SourceFile:94)
	at xz.D(SourceFile:580)
	at oc.l_(SourceFile:1159)
	at ua.l_(SourceFile:203)
	at js.h(SourceFile:180)
	at jx.a(SourceFile:205)
	at et.a(SourceFile:136)
	at cm.b(SourceFile:64)
	at jx.d(SourceFile:59)
	at ka.b(SourceFile:37)
	at bkr.b(SourceFile:84)
	at net.minecraft.server.MinecraftServer.t(SourceFile:488)
	at net.minecraft.server.MinecraftServer.s(SourceFile:405)
	at bko.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:339)
	at hf.run(SourceFile:582)


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

-- Head --
Stacktrace:
	at org.apache.commons.lang3.Validate.notEmpty(Validate.java:398)
	at oq.<init>(SourceFile:31)
	at tm.a(SourceFile:94)
	at xz.D(SourceFile:580)
	at oc.l_(SourceFile:1159)
	at ua.l_(SourceFile:203)

-- Player being ticked --
Details:
	Entity Type: null (js)
	Entity ID: 13
	Entity Name: grimwaco
	Entity's Exact location: -217.75, 4.00, -185.59
	Entity's Block location: World: (-218,4,-186), Chunk: (at 6,0,6 in -14,-12; contains blocks -224,0,-192 to -209,255,-177), Region: (-1,-1; contains chunks -32,-32 to -1,-1, blocks -512,0,-512 to -1,255,-1)
	Entity's Momentum: 0.00, -0.08, 0.00
Stacktrace:
	at js.h(SourceFile:180)
	at jx.a(SourceFile:205)
	at et.a(SourceFile:136)
	at cm.b(SourceFile:64)
	at jx.d(SourceFile:59)

-- Ticking connection --
Details:
	Connection: jx@d7785cb
Stacktrace:
	at ka.b(SourceFile:37)
	at bkr.b(SourceFile:84)
	at net.minecraft.server.MinecraftServer.t(SourceFile:488)
	at net.minecraft.server.MinecraftServer.s(SourceFile:405)
	at bko.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:339)
	at hf.run(SourceFile:582)

-- System Details --
Details:
	Minecraft Version: 1.6.1
	Operating System: Windows 8 (amd64) version 6.2
	Java Version: 1.7.0_17, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 348363232 bytes (332 MB) / 498794496 bytes (475 MB) up to 954466304 bytes (910 MB)
	JVM Flags: 1 total; -Xmx1G
	AABB Pool Size: 238 (13328 bytes; 0 MB) allocated, 230 (12880 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 25 (1400 bytes; 0 MB) allocated, 25 (1400 bytes; 0 MB) used
	Player Count: 1 / 8; [js['grimwaco'/13, l='testit', x=-217.75, y=4.00, z=-185.59]]
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.