Hopper: java.lang.IllegalArgumentException: n must be positive

This is an automatically generated report based from the following crash: http://hopper.minecraft.net/crashes/minecraft/MCX-57921/

Crash:

java.lang.IllegalArgumentException: n must be positive
	at java.util.Random.nextInt(Unknown Source)
	at aav.a(SourceFile:144)
	at oe.c(SourceFile:800)
	at ue.d(SourceFile:737)
	at oe.a(SourceFile:563)
	at ue.a(SourceFile:694)
	at ju.a(SourceFile:262)
	at ul.a(SourceFile:29)
	at ui.l_(SourceFile:142)
	at abv.a(SourceFile:1349)
	at jr.a(SourceFile:479)
	at abv.g(SourceFile:1327)

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

---- Minecraft Crash Report ----
// Don't do that.

Time: 8/15/13 4:15 PM
Description: Ticking entity

java.lang.IllegalArgumentException: n must be positive
	at java.util.Random.nextInt(Unknown Source)
	at aav.a(SourceFile:144)
	at oe.c(SourceFile:800)
	at ue.d(SourceFile:737)
	at oe.a(SourceFile:563)
	at ue.a(SourceFile:694)
	at ju.a(SourceFile:262)
	at ul.a(SourceFile:29)
	at ui.l_(SourceFile:142)
	at abv.a(SourceFile:1349)
	at jr.a(SourceFile:479)
	at abv.g(SourceFile:1327)
	at abv.h(SourceFile:1234)
	at jr.h(SourceFile:364)
	at net.minecraft.server.MinecraftServer.t(SourceFile:470)
	at net.minecraft.server.MinecraftServer.s(SourceFile:405)
	at bkw.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:339)
	at hh.run(SourceFile:582)


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

-- Head --
Stacktrace:
	at java.util.Random.nextInt(Unknown Source)
	at aav.a(SourceFile:144)
	at oe.c(SourceFile:800)
	at ue.d(SourceFile:737)
	at oe.a(SourceFile:563)
	at ue.a(SourceFile:694)
	at ju.a(SourceFile:262)
	at ul.a(SourceFile:29)
	at ui.l_(SourceFile:142)
	at abv.a(SourceFile:1349)
	at jr.a(SourceFile:479)
	at abv.g(SourceFile:1327)

-- Entity being ticked --
Details:
	Entity Type: Fireball (ul)
	Entity ID: 392
	Entity Name: Fireball
	Entity's Exact location: -237.80, 37.76, -138.59
	Entity's Block location: World: (-238,37,-139), Chunk: (at 2,2,5 in -15,-9; contains blocks -240,0,-144 to -225,255,-129), Region: (-1,-1; contains chunks -32,-32 to -1,-1, blocks -512,0,-512 to -1,255,-1)
	Entity's Momentum: 1.06, -0.20, -1.37
Stacktrace:
	at abv.h(SourceFile:1234)
	at jr.h(SourceFile:364)

-- Affected level --
Details:
	Level name: REECE World
	All players: 1 total; [ju['CadvanTheCreator'/195, l='REECE World', x=-237.26, y=36.00, z=-139.27]]
	Chunk stats: ServerChunkCache: 472 Drop: 0
	Level seed: 8708785005044202063
	Level generator: ID 00 - default, ver 1. Features enabled: false
	Level generator options: 
	Level spawn location: World: (0,0,0), Chunk: (at 0,0,0 in 0,0; contains blocks 0,0,0 to 15,255,15), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
	Level time: 0 game time, 0 day time
	Level dimension: 0
	Level storage version: 0x00000 - Unknown?
	Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
	Level game mode: ~~ERROR~~ NullPointerException: null
Stacktrace:
	at net.minecraft.server.MinecraftServer.t(SourceFile:470)
	at net.minecraft.server.MinecraftServer.s(SourceFile:405)
	at bkw.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:339)
	at hh.run(SourceFile:582)

-- System Details --
Details:
	Minecraft Version: 1.6.2
	Operating System: Windows 8 (x86) version 6.2
	Java Version: 1.7.0_25, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Oracle Corporation
	Memory: 40597536 bytes (38 MB) / 201756672 bytes (192 MB) up to 518979584 bytes (494 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
	AABB Pool Size: 4442 (248752 bytes; 0 MB) allocated, 3376 (189056 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 1, tallocated: 63
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 387 (21672 bytes; 0 MB) allocated, 375 (21000 bytes; 0 MB) used
	Player Count: 1 / 8; [ju['CadvanTheCreator'/195, l='REECE World', x=-237.26, y=36.00, z=-139.27]]
	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-57921/3168266/