Hopper: java.lang.IllegalArgumentException: Comparison method violates its general contract!

This is an automatically generated report based from the following crash: http://hopper.minecraft.net/crashes/minecraft/MCX-466716/

Crash:

java.lang.IllegalArgumentException: Comparison method violates its general contract!
	at java.util.TimSort.mergeLo(Unknown Source)
	at java.util.TimSort.mergeAt(Unknown Source)
	at java.util.TimSort.mergeCollapse(Unknown Source)
	at java.util.TimSort.sort(Unknown Source)
	at java.util.TimSort.sort(Unknown Source)
	at java.util.Arrays.sort(Unknown Source)
	at bls.a(SourceFile:515)
	at bll.a(SourceFile:974)

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

---- Minecraft Crash Report ----
// This is a token for 1 free hug. Redeem at your nearest Mojangsta: [~~HUG~~]

Time: 25.10.13 17:50
Description: Unexpected error

java.lang.IllegalArgumentException: Comparison method violates its general contract!
	at java.util.TimSort.mergeLo(Unknown Source)
	at java.util.TimSort.mergeAt(Unknown Source)
	at java.util.TimSort.mergeCollapse(Unknown Source)
	at java.util.TimSort.sort(Unknown Source)
	at java.util.TimSort.sort(Unknown Source)
	at java.util.Arrays.sort(Unknown Source)
	at bls.a(SourceFile:515)
	at bll.a(SourceFile:974)
	at bll.b(SourceFile:815)
	at azd.ad(SourceFile:780)
	at azd.e(SourceFile:704)
	at net.minecraft.client.main.Main.main(SourceFile:103)


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

-- Head --
Stacktrace:
	at java.util.TimSort.mergeLo(Unknown Source)
	at java.util.TimSort.mergeAt(Unknown Source)
	at java.util.TimSort.mergeCollapse(Unknown Source)
	at java.util.TimSort.sort(Unknown Source)
	at java.util.TimSort.sort(Unknown Source)
	at java.util.Arrays.sort(Unknown Source)
	at bls.a(SourceFile:515)
	at bll.a(SourceFile:974)

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [bje['freddymaster1998'/7207, l='MpServer', x=-151,70, y=64,00, z=310,70]]
	Chunk stats: MultiplayerChunkCache: 352, 352
	Level seed: 0
	Level generator: ID 00 - default, ver 1. Features enabled: false
	Level generator options: 
	Level spawn location: World: (-92,64,256), Chunk: (at 4,4,0 in -6,16; contains blocks -96,0,256 to -81,255,271), Region: (-1,0; contains chunks -32,0 to -1,31, blocks -512,0,0 to -1,255,511)
	Level time: 9599 game time, 9599 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: Game mode: creative (ID 1). Hardcore: false. Cheats: false
	Forced entities: 79 total; [wz['Spider'/47769, l='MpServer', x=-90,50, y=35,00, z=339,50], xc['Zombie'/46679, l='MpServer', x=-76,50, y=17,00, z=325,50], wx['Skeleton'/45052, l='MpServer', x=-83,41, y=18,00, z=286,91], wz['Spider'/42856, l='MpServer', x=-169,50, y=33,00, z=339,50], wl['Creeper'/42857, l='MpServer', x=-170,84, y=33,00, z=346,75], wx['Skeleton'/45045, l='MpServer', x=-141,50, y=50,00, z=318,50], uq['Bat'/43909, l='MpServer', x=-170,56, y=29,20, z=276,07], uq['Bat'/43911, l='MpServer', x=-176,32, y=29,01, z=275,30], uq['Bat'/43910, l='MpServer', x=-167,83, y=28,78, z=287,85], xc['Zombie'/19516, l='MpServer', x=-113,22, y=41,00, z=322,22], wl['Creeper'/42817, l='MpServer', x=-71,50, y=20,00, z=342,50], wl['Creeper'/42818, l='MpServer', x=-71,50, y=20,00, z=344,50], ve['Squid'/26159, l='MpServer', x=-120,59, y=47,00, z=361,13], wl['Creeper'/45787, l='MpServer', x=-155,50, y=33,00, z=232,50], wl['Creeper'/45786, l='MpServer', x=-77,50, y=52,00, z=230,50], wl['Creeper'/45785, l='MpServer', x=-87,09, y=51,00, z=228,53], wx['Skeleton'/45784, l='MpServer', x=-82,50, y=24,00, z=343,50], ve['Squid'/26115, l='MpServer', x=-186,47, y=57,34, z=359,19], xc['Zombie'/46782, l='MpServer', x=-79,81, y=34,00, z=331,63], xc['Zombie'/46775, l='MpServer', x=-177,50, y=33,00, z=323,50], xc['Zombie'/46774, l='MpServer', x=-178,50, y=33,00, z=321,50], uq['Bat'/47646, l='MpServer', x=-164,25, y=34,00, z=328,16], uq['Bat'/47647, l='MpServer', x=-164,84, y=34,08, z=323,06], xc['Zombie'/39961, l='MpServer', x=-174,50, y=39,00, z=364,50], wx['Skeleton'/23949, l='MpServer', x=-86,50, y=12,00, z=311,50], uq['Bat'/47652, l='MpServer', x=-178,09, y=30,00, z=275,75], uq['Bat'/47649, l='MpServer', x=-164,50, y=34,00, z=326,50], uq['Bat'/47651, l='MpServer', x=-181,94, y=31,00, z=271,34], xc['Zombie'/37083, l='MpServer', x=-71,50, y=37,00, z=343,50], uq['Bat'/47650, l='MpServer', x=-164,50, y=34,05, z=328,56], wm['Enderman'/33875, l='MpServer', x=-174,50, y=39,00, z=356,50], uq['Bat'/39352, l='MpServer', x=-195,94, y=15,00, z=372,75], wx['Skeleton'/45945, l='MpServer', x=-214,50, y=15,00, z=258,50], bje['freddymaster1998'/7207, l='MpServer', x=-151,70, y=64,00, z=310,70], wx['Skeleton'/45943, l='MpServer', x=-134,50, y=16,00, z=350,50], xc['Zombie'/22703, l='MpServer', x=-155,09, y=54,00, z=326,50], wx['Skeleton'/38362, l='MpServer', x=-157,50, y=39,00, z=353,50], xc['Zombie'/39188, l='MpServer', x=-78,50, y=33,00, z=349,50], wx['Skeleton'/43479, l='MpServer', x=-170,13, y=28,00, z=288,34], wx['Skeleton'/43480, l='MpServer', x=-168,50, y=28,00, z=284,50], wx['Skeleton'/43481, l='MpServer', x=-169,59, y=28,00, z=289,28], xc['Zombie'/45098, l='MpServer', x=-204,50, y=22,00, z=373,50], xc['Zombie'/45102, l='MpServer', x=-101,50, y=26,00, z=250,50], xc['Zombie'/42329, l='MpServer', x=-119,06, y=43,00, z=320,38], xc['Zombie'/42330, l='MpServer', x=-108,22, y=40,00, z=322,50], vy['entity.MinecartChest.name'/7131, l='MpServer', x=-183,50, y=31,50, z=342,50], uq['Bat'/43416, l='MpServer', x=-132,25, y=17,51, z=363,59], uq['Bat'/43419, l='MpServer', x=-158,88, y=31,30, z=244,22], uq['Bat'/43420, l='MpServer', x=-159,00, y=32,07, z=245,41], wx['Skeleton'/38426, l='MpServer', x=-112,88, y=46,00, z=234,56], ut['Cow'/7144, l='MpServer', x=-117,97, y=73,00, z=305,94], ut['Cow'/7145, l='MpServer', x=-95,53, y=75,00, z=301,23], ut['Cow'/7146, l='MpServer', x=-99,72, y=67,00, z=310,50], ut['Cow'/7147, l='MpServer', x=-92,25, y=76,00, z=290,31], ut['Cow'/7148, l='MpServer', x=-95,13, y=76,00, z=293,03], us['Chicken'/7137, l='MpServer', x=-91,47, y=82,00, z=246,47], us['Chicken'/7138, l='MpServer', x=-87,53, y=79,00, z=236,47], us['Chicken'/7139, l='MpServer', x=-96,44, y=82,00, z=228,59], us['Chicken'/7140, l='MpServer', x=-87,59, y=78,00, z=251,34], ut['Cow'/7141, l='MpServer', x=-85,78, y=75,00, z=283,78], ut['Cow'/7143, l='MpServer', x=-102,91, y=76,00, z=287,06], uq['Bat'/25610, l='MpServer', x=-120,69, y=14,10, z=238,41], wx['Skeleton'/46260, l='MpServer', x=-85,50, y=38,00, z=229,50], xc['Zombie'/46219, l='MpServer', x=-144,44, y=51,00, z=321,08], wl['Creeper'/46222, l='MpServer', x=-84,31, y=33,95, z=335,65], uq['Bat'/36690, l='MpServer', x=-176,25, y=34,10, z=323,88], wm['Enderman'/29004, l='MpServer', x=-84,50, y=17,00, z=288,22], wl['Creeper'/29006, l='MpServer', x=-78,16, y=34,00, z=333,88], uq['Bat'/46375, l='MpServer', x=-88,25, y=18,10, z=240,63], uq['Bat'/46374, l='MpServer', x=-88,08, y=15,07, z=233,96], uq['Bat'/46372, l='MpServer', x=-93,91, y=30,20, z=321,88], wx['Skeleton'/43241, l='MpServer', x=-72,38, y=22,00, z=297,69], xc['Zombie'/46403, l='MpServer', x=-95,50, y=38,00, z=308,50], xc['Zombie'/46402, l='MpServer', x=-96,50, y=38,00, z=308,50], xc['Zombie'/46480, l='MpServer', x=-122,50, y=43,00, z=230,50], xc['Zombie'/46478, l='MpServer', x=-121,50, y=43,00, z=233,50], xc['Zombie'/46479, l='MpServer', x=-122,50, y=43,00, z=232,50], wx['Skeleton'/43008, l='MpServer', x=-188,50, y=12,00, z=367,50], wl['Creeper'/43009, l='MpServer', x=-190,69, y=12,00, z=370,69]]
	Retry entities: 0 total; []
	Server brand: vanilla
	Server type: Integrated singleplayer server
Stacktrace:
	at biz.a(SourceFile:284)
	at azd.b(SourceFile:1951)
	at azd.e(SourceFile:718)
	at net.minecraft.client.main.Main.main(SourceFile:103)

-- System Details --
Details:
	Minecraft Version: 1.7.2
	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: 59609832 bytes (56 MB) / 315301888 bytes (300 MB) up to 518979584 bytes (494 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
	AABB Pool Size: 2653 (148568 bytes; 0 MB) allocated, 2352 (131712 bytes; 0 MB) used
	IntCache: cache: 0, tcache: 0, allocated: 12, tallocated: 94
	Launched Version: 1.7.2
	LWJGL: 2.9.0
	OpenGL: GeForce GTX 560/PCIe/SSE2 GL version 4.3.0, NVIDIA Corporation
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Packs: []
	Current Language: English (US)
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 2004 (112224 bytes; 0 MB) allocated, 383 (21448 bytes; 0 MB) used
	Anisotropic Filtering: Off (1)

You can see this full report at http://hopper.minecraft.net/crashes/minecraft/MCX-466716/21393205/