The game crashed after I was making maps bigger.

Put the summary of the bug you're having here
The game would crash when I was making maps bigger
What I expected to happen was...:
Describe what you thought should happen here
I was on the ShadowBlockz server and I decided to make a big map of the creative plots on that server. I made a map and got lots of paper. I clicked on the crafting table and arranged the paper and the map so I could make it bigger.
What actually happened was...:
Describe what happened here
After doing this 3 or four times, the game crashed and told me to report this to Mojang.
Steps to Reproduce:
1. Go on the ShadowBlockz server
2. Get a creative plot
3. Set down a crafting table
4. Right click an empty map.
5. Try to make it into a bigger map several times in the crafting table by surrounding the map with paper.

When the game crashed, this is the error list I got:

---- Minecraft Crash Report ----
// Surprise! Haha. Well, this is awkward.

Time: 7/3/13 3:19 PM
Description: Updating screen events

java.lang.NullPointerException
	at yc.d(SourceFile:235)
	at xz.a(SourceFile:324)
	at vy.b(SourceFile:41)
	at vy.a(SourceFile:58)
	at ut.a(SourceFile:239)
	at bct.a(SourceFile:295)
	at awp.a(SourceFile:582)
	at awp.a(SourceFile:410)
	at avv.d(SourceFile:125)
	at avv.m(SourceFile:109)
	at atn.k(SourceFile:1157)
	at atn.S(SourceFile:662)
	at atn.d(SourceFile:618)
	at net.minecraft.client.main.Main.main(SourceFile:101)


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

-- Head --
Stacktrace:
	at yc.d(SourceFile:235)
	at xz.a(SourceFile:324)
	at vy.b(SourceFile:41)
	at vy.a(SourceFile:58)
	at ut.a(SourceFile:239)
	at bct.a(SourceFile:295)
	at awp.a(SourceFile:582)
	at awp.a(SourceFile:410)
	at avv.d(SourceFile:125)
	at avv.m(SourceFile:109)

-- Affected screen --
Details:
	Screen name: axb

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [bcx['bluestarcool'/2171, l='MpServer', x=-355.25, y=66.62, z=276.10]]
	Chunk stats: MultiplayerChunkCache: 441
	Level seed: 0
	Level generator: ID 00 - default, ver 1. Features enabled: false
	Level generator options: 
	Level spawn location: World: (31,69,31), Chunk: (at 15,4,15 in 1,1; contains blocks 16,0,16 to 31,255,31), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
	Level time: 67748035 game time, 67968961 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: 2 total; [rp['Banana'/23639862, l='MpServer', x=-386.41, y=65.00, z=239.13], bcx['bluestarcool'/2171, l='MpServer', x=-355.25, y=66.62, z=276.10]]
	Retry entities: 0 total; []
Stacktrace:
	at bcu.a(SourceFile:284)
	at atn.b(SourceFile:1743)
	at atn.d(SourceFile:627)
	at net.minecraft.client.main.Main.main(SourceFile:101)

-- System Details --
Details:
	Minecraft Version: 1.6.1
	Operating System: Windows 8 (x86) version 6.2
	Java Version: 1.7.0_21, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Oracle Corporation
	Memory: 9243880 bytes (8 MB) / 106774528 bytes (101 MB) up to 1037959168 bytes (989 MB)
	JVM Flags: 1 total; -Xmx1G
	AABB Pool Size: 33297 (1864632 bytes; 1 MB) allocated, 2 (112 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 3, tallocated: 63
	Launched Version: 1.6.1
	LWJGL: 2.9.0
	OpenGL: Intel(R) HD Graphics 4000 GL version 4.0.0 - Build 9.17.10.2849, Intel
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Pack: Default
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 652 (36512 bytes; 0 MB) allocated, 15 (840 bytes; 0 MB) used