Hopper: java.lang.NullPointerException: Batching chunks

java.lang.NullPointerException: Batching chunks
	at cif.at(SourceFile:481)

---- Minecraft Crash Report ----
// I just don't know what went wrong :(

Time: 8/8/14 1:04 PM
Description: Batching chunks

java.lang.NullPointerException: Batching chunks
	at cif.at(SourceFile:481)
	at agw.aO(SourceFile:1793)
	at cny.a(SourceFile:66)
	at cny.run(SourceFile:31)
	at java.lang.Thread.run(Unknown Source)


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

-- Head --
Stacktrace:
	at cif.at(SourceFile:481)

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [cif['SwiftArrow1000'/302, l='MpServer', x=60.50, y=136.10, z=247.50]]
	Chunk stats: MultiplayerChunkCache: 10, 10
	Level seed: 0
	Level generator: ID 00 - default, ver 1. Features enabled: false
	Level generator options: 
	Level spawn location: 72.00,64.00,252.00 - World: (72,64,252), Chunk: (at 8,4,12 in 4,15; contains blocks 64,0,240 to 79,255,255), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
	Level time: 14272 game time, 27034 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: 20 total; [agc['Zombie'/338076, l='MpServer', x=110.50, y=24.00, z=249.50], cif['SwiftArrow1000'/302, l='MpServer', x=65.97, y=85.00, z=240.17], abo['Chicken'/119, l='MpServer', x=55.50, y=85.00, z=241.50], abo['Chicken'/117, l='MpServer', x=54.50, y=65.00, z=243.50], abo['Chicken'/130, l='MpServer', x=59.41, y=69.00, z=246.59], abl['Bat'/476103, l='MpServer', x=119.38, y=46.91, z=249.50], afx['Spider'/446913, l='MpServer', x=78.50, y=68.00, z=210.50], acj['Squid'/440172, l='MpServer', x=129.47, y=61.00, z=241.47], cif['SwiftArrow1000'/302, l='MpServer', x=67.49, y=89.00, z=246.92], cif['SwiftArrow1000'/302, l='MpServer', x=58.53, y=67.00, z=253.52], cif['SwiftArrow1000'/302, l='MpServer', x=60.50, y=136.10, z=247.50], cif['SwiftArrow1000'/302, l='MpServer', x=68.17, y=85.00, z=240.52], adp['item.item.egg'/258813, l='MpServer', x=84.94, y=69.00, z=204.22], agc['Zombie'/401334, l='MpServer', x=138.50, y=52.00, z=218.50], cif['SwiftArrow1000'/302, l='MpServer', x=66.53, y=85.00, z=243.40], cif['SwiftArrow1000'/302, l='MpServer', x=59.69, y=85.00, z=246.16], agc['Zombie'/455056, l='MpServer', x=83.34, y=62.00, z=196.34], abl['Bat'/463897, l='MpServer', x=96.13, y=46.02, z=242.44], aei['Creeper'/285277, l='MpServer', x=110.41, y=27.00, z=263.78], agc['Zombie'/455051, l='MpServer', x=87.97, y=61.00, z=182.56]]
	Retry entities: ~~ERROR~~ ConcurrentModificationException: null
	Server brand: vanilla
	Server type: Integrated singleplayer server
Stacktrace:
	at cee.a(SourceFile:308)
	at bsn.b(SourceFile:2255)
	at cny.run(SourceFile:37)
	at java.lang.Thread.run(Unknown Source)

-- System Details --
Details:
	Minecraft Version: 14w32d
	Operating System: Windows 7 (amd64) version 6.1
	Java Version: 1.7.0_13, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 487752376 bytes (465 MB) / 791142400 bytes (754 MB) up to 1060372480 bytes (1011 MB)
	JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
	IntCache: cache: 0, tcache: 60, allocated: 13, tallocated: 95
	Launched Version: 14w32d
	LWJGL: 2.9.1
	OpenGL: ~~ERROR~~ RuntimeException: No OpenGL context found in the current thread.
	GL Caps: Using GL 1.3 multitexturing.
Using GL 1.3 texture combiners.
Using framebuffer objects because OpenGL 3.0 is supported and separate blending is supported.
Shaders are available because OpenGL 2.1 is supported.
VBOs are available because OpenGL 1.5 is supported.

	Using VBOs: No
	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)