Custom Trading Crashes Client

This bug can be replicated by creating a Villager with a custom trade offer.

1. Find Villager.
2. Open Trade UI.
3. Put an item in one of the trade slots.
4. Watch your game crash.

And a crash report!

---- Minecraft Crash Report ----
// Shall we play a game?

Time: 10/25/13 4:58 PM
Description: Updating screen events

java.lang.NullPointerException: Updating screen events
	at afa.a(SourceFile:36)
	at ze.h(SourceFile:135)
	at ze.a(SourceFile:77)
	at zk.c(SourceFile:77)
	at ye.a(SourceFile:157)
	at biy.a(SourceFile:308)
	at bdd.a(SourceFile:490)
	at bdd.b(SourceFile:455)
	at bcd.d(SourceFile:240)
	at bcd.k(SourceFile:211)
	at azd.o(SourceFile:1303)
	at azd.ad(SourceFile:753)
	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 afa.a(SourceFile:36)
	at ze.h(SourceFile:135)
	at ze.a(SourceFile:77)
	at zk.c(SourceFile:77)
	at ye.a(SourceFile:157)
	at biy.a(SourceFile:308)
	at bdd.a(SourceFile:490)
	at bdd.b(SourceFile:455)
	at bcd.d(SourceFile:240)
	at bcd.k(SourceFile:211)

-- Affected screen --
Details:
	Screen name: beb

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [bje['p197'/2, l='MpServer', x=-271.95, y=44.62, z=865.42]]
	Chunk stats: MultiplayerChunkCache: 299, 299
	Level seed: 0
	Level generator: ID 00 - default, ver 1. Features enabled: false
	Level generator options: 
	Level spawn location: World: (-709,63,-107), Chunk: (at 11,3,5 in -45,-7; contains blocks -720,0,-112 to -705,255,-97), Region: (-2,-1; contains chunks -64,-32 to -33,-1, blocks -1024,0,-512 to -513,255,-1)
	Level time: 2750966 game time, 5156 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: 81 total; [wx['Skeleton'/9771, l='MpServer', x=-258.50, y=22.00, z=863.50], uq['Bat'/7423, l='MpServer', x=-345.06, y=9.79, z=920.59], wl['Creeper'/7897, l='MpServer', x=-302.50, y=32.00, z=926.50], wx['Skeleton'/9491, l='MpServer', x=-239.50, y=31.00, z=827.50], wl['Creeper'/8536, l='MpServer', x=-305.03, y=32.00, z=927.50], wl['Creeper'/9492, l='MpServer', x=-236.50, y=31.00, z=831.50], xc['Zombie'/7902, l='MpServer', x=-302.50, y=32.00, z=928.50], xc['Zombie'/11950, l='MpServer', x=-251.55, y=26.47, z=846.29], wl['Creeper'/9042, l='MpServer', x=-264.44, y=24.00, z=857.00], uq['Bat'/8167, l='MpServer', x=-272.30, y=1.67, z=847.95], wx['Skeleton'/9527, l='MpServer', x=-260.70, y=26.00, z=847.50], xc['Zombie'/11205, l='MpServer', x=-237.50, y=28.00, z=846.50], xc['Zombie'/11204, l='MpServer', x=-245.23, y=27.00, z=839.30], wl['Creeper'/10107, l='MpServer', x=-262.50, y=23.00, z=857.50], wx['Skeleton'/9833, l='MpServer', x=-255.13, y=21.00, z=841.44], xc['Zombie'/12260, l='MpServer', x=-333.16, y=33.00, z=918.84], xc['Zombie'/9020, l='MpServer', x=-257.52, y=26.00, z=847.50], wx['Skeleton'/12028, l='MpServer', x=-257.50, y=21.00, z=863.50], xc['Zombie'/11169, l='MpServer', x=-288.50, y=38.00, z=849.03], wx['Skeleton'/11168, l='MpServer', x=-289.69, y=38.00, z=849.69], wl['Creeper'/11463, l='MpServer', x=-247.00, y=23.00, z=859.44], bje['p197'/2, l='MpServer', x=-271.95, y=44.62, z=865.42], wx['Skeleton'/11465, l='MpServer', x=-323.50, y=16.00, z=910.50], wl['Creeper'/10671, l='MpServer', x=-263.50, y=19.00, z=854.50], wx['Skeleton'/9807, l='MpServer', x=-254.50, y=28.00, z=845.50], uq['Bat'/8480, l='MpServer', x=-280.81, y=28.10, z=838.94], xc['Zombie'/11972, l='MpServer', x=-231.50, y=33.00, z=893.50], wx['Skeleton'/10051, l='MpServer', x=-252.50, y=31.00, z=848.50], wx['Skeleton'/8970, l='MpServer', x=-259.55, y=27.00, z=846.12], wx['Skeleton'/10564, l='MpServer', x=-259.35, y=23.00, z=857.55], xc['Zombie'/10565, l='MpServer', x=-264.47, y=24.00, z=860.09], wl['Creeper'/9890, l='MpServer', x=-257.50, y=22.00, z=857.50], wl['Creeper'/11283, l='MpServer', x=-300.50, y=32.00, z=925.50], wl['Creeper'/11282, l='MpServer', x=-298.50, y=32.00, z=924.50], wl['Creeper'/11285, l='MpServer', x=-304.50, y=32.00, z=928.50], wx['Skeleton'/11284, l='MpServer', x=-303.50, y=32.00, z=930.50], wm['Enderman'/12095, l='MpServer', x=-297.50, y=32.00, z=926.50], xc['Zombie'/9601, l='MpServer', x=-249.66, y=16.00, z=851.34], wm['Enderman'/12094, l='MpServer', x=-294.94, y=31.00, z=927.94], wx['Skeleton'/11546, l='MpServer', x=-246.69, y=30.03, z=857.32], uq['Bat'/8031, l='MpServer', x=-295.26, y=33.58, z=918.30], wx['Skeleton'/11551, l='MpServer', x=-345.50, y=34.00, z=846.50], wl['Creeper'/11537, l='MpServer', x=-266.50, y=18.00, z=846.50], wx['Skeleton'/11552, l='MpServer', x=-344.50, y=34.00, z=845.50], xc['Zombie'/9874, l='MpServer', x=-248.72, y=27.00, z=843.31], wx['Skeleton'/9397, l='MpServer', x=-254.69, y=21.00, z=842.63], wl['Creeper'/7226, l='MpServer', x=-350.50, y=21.00, z=837.50], xc['Zombie'/9685, l='MpServer', x=-242.06, y=31.00, z=846.38], wx['Skeleton'/11040, l='MpServer', x=-236.50, y=29.00, z=841.50], wl['Creeper'/9423, l='MpServer', x=-352.50, y=20.00, z=840.50], wl['Creeper'/9422, l='MpServer', x=-350.50, y=20.00, z=840.50], wl['Creeper'/9421, l='MpServer', x=-352.50, y=20.00, z=838.50], wl['Creeper'/9420, l='MpServer', x=-351.50, y=20.00, z=839.50], uq['Bat'/10527, l='MpServer', x=-246.55, y=31.10, z=851.75], uq['Bat'/10526, l='MpServer', x=-243.78, y=23.51, z=828.00], wl['Creeper'/9716, l='MpServer', x=-270.13, y=17.00, z=849.69], uq['Bat'/7741, l='MpServer', x=-270.17, y=23.85, z=903.90], us['Chicken'/7013, l='MpServer', x=-347.44, y=39.00, z=905.59], wx['Skeleton'/9714, l='MpServer', x=-274.09, y=17.00, z=846.50], wx['Skeleton'/9715, l='MpServer', x=-268.50, y=17.00, z=847.50], rf['entity.ItemFrame.name'/7015, l='MpServer', x=-390.50, y=85.50, z=851.06], rf['entity.ItemFrame.name'/7014, l='MpServer', x=-390.50, y=78.50, z=848.06], uq['Bat'/7426, l='MpServer', x=-319.65, y=4.18, z=923.59], us['Chicken'/7016, l='MpServer', x=-344.44, y=41.00, z=919.47], uq['Bat'/7425, l='MpServer', x=-335.05, y=17.57, z=922.05], uq['Bat'/7424, l='MpServer', x=-327.45, y=9.86, z=933.11], uq['Bat'/8357, l='MpServer', x=-345.40, y=5.84, z=851.51], us['Chicken'/7021, l='MpServer', x=-283.47, y=41.00, z=870.66], wl['Creeper'/12101, l='MpServer', x=-315.59, y=25.00, z=896.00], rf['entity.ItemFrame.name'/7020, l='MpServer', x=-276.50, y=45.50, z=859.94], va['Pig'/7023, l='MpServer', x=-339.81, y=46.00, z=801.53], va['Pig'/7022, l='MpServer', x=-280.91, y=39.00, z=870.50], us['Chicken'/7024, l='MpServer', x=-329.56, y=42.00, z=804.56], us['Chicken'/7025, l='MpServer', x=-329.56, y=45.00, z=824.47], va['Pig'/7026, l='MpServer', x=-318.50, y=42.00, z=806.25], va['Pig'/7027, l='MpServer', x=-324.50, y=44.00, z=837.97], ut['Cow'/7028, l='MpServer', x=-345.22, y=44.00, z=853.16], xc['Zombie'/11036, l='MpServer', x=-240.50, y=29.00, z=835.50], wx['Skeleton'/11039, l='MpServer', x=-240.50, y=29.00, z=837.50], wx['Skeleton'/11038, l='MpServer', x=-243.06, y=29.00, z=827.66], xh['Villager'/7036, l='MpServer', x=-271.59, y=43.00, z=868.31]]
	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:713)
	at net.minecraft.client.main.Main.main(SourceFile:103)

-- System Details --
Details:
	Minecraft Version: 1.7.2
	Operating System: Mac OS X (x86_64) version 10.7.5
	Java Version: 1.6.0_51, Apple Inc.
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Apple Inc.
	Memory: 54838040 bytes (52 MB) / 185909248 bytes (177 MB) up to 1065025536 bytes (1015 MB)
	JVM Flags: 1 total; -Xmx1G
	AABB Pool Size: 7091 (397096 bytes; 0 MB) allocated, 3 (168 bytes; 0 MB) used
	IntCache: cache: 0, tcache: 0, allocated: 12, tallocated: 94
	Launched Version: 1.7.2
	LWJGL: 2.9.1
	OpenGL: AMD Radeon HD 6750M OpenGL Engine GL version 2.1 ATI-7.32.12, ATI Technologies Inc.
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Packs: [Minecraft Alpha 1-converted-1375480610273]
	Current Language: English (US)
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 291 (16296 bytes; 0 MB) allocated, 23 (1288 bytes; 0 MB) used
	Anisotropic Filtering: Off (1)