Hopper: java.lang.NullPointerException - Custom Villager Trading

This is an automatically generated report based from the following crash: http://hopper.minecraft.net/crashes/minecraft/MCX-198069/

Crash:

java.lang.NullPointerException
	at acu.a(SourceFile:36)
	at wy.h(SourceFile:135)
	at wy.a(SourceFile:77)
	at xe.c(SourceFile:77)
	at vy.a(SourceFile:222)
	at bgb.a(SourceFile:296)
	at baq.a(SourceFile:490)
	at baq.b(SourceFile:463)
	at azq.d(SourceFile:240)
	at azq.m(SourceFile:211)

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

---- Minecraft Crash Report ----
// Hey, that tickles! Hehehe!

Time: 9/20/13 5:48 PM
Description: Updating screen events

java.lang.NullPointerException
	at acu.a(SourceFile:36)
	at wy.h(SourceFile:135)
	at wy.a(SourceFile:77)
	at xe.c(SourceFile:77)
	at vy.a(SourceFile:222)
	at bgb.a(SourceFile:296)
	at baq.a(SourceFile:490)
	at baq.b(SourceFile:463)
	at azq.d(SourceFile:240)
	at azq.m(SourceFile:211)
	at awp.o(SourceFile:1256)
	at awp.aa(SourceFile:726)
	at awp.e(SourceFile:677)
	at net.minecraft.client.main.Main.main(SourceFile:104)


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

-- Head --
Stacktrace:
	at acu.a(SourceFile:36)
	at wy.h(SourceFile:135)
	at wy.a(SourceFile:77)
	at xe.c(SourceFile:77)
	at vy.a(SourceFile:222)
	at bgb.a(SourceFile:296)
	at baq.a(SourceFile:490)
	at baq.b(SourceFile:463)
	at azq.d(SourceFile:240)
	at azq.m(SourceFile:211)

-- Affected screen --
Details:
	Screen name: bbo

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [bgh['Skycrafter231'/270, l='MpServer', x=-117.30, y=120.62, z=6.40]]
	Chunk stats: MultiplayerChunkCache: 225, 225
	Level seed: 0
	Level generator: ID 03 - amplified, ver 0. Features enabled: false
	Level generator options: 
	Level spawn location: World: (4,64,136), Chunk: (at 4,4,8 in 0,8; contains blocks 0,0,128 to 15,255,143), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
	Level time: 143395 game time, 154745 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: 115 total; [ug['Creeper'/0, l='MpServer', x=-183.50, y=53.00, z=-4.94], us['Skeleton'/1, l='MpServer', x=-180.50, y=56.00, z=-3.91], sx['Pig'/2, l='MpServer', x=-176.50, y=110.00, z=-3.69], sx['Pig'/3, l='MpServer', x=-177.44, y=111.00, z=6.38], sx['Pig'/4, l='MpServer', x=-178.50, y=120.00, z=4.50], sn['Bat'/5, l='MpServer', x=-179.28, y=49.11, z=72.09], sn['Bat'/6, l='MpServer', x=-164.53, y=50.89, z=-47.34], ut['Slime'/7, l='MpServer', x=-171.69, y=37.00, z=-27.31], sq['Cow'/8, l='MpServer', x=-163.75, y=116.00, z=-20.69], ug['Creeper'/9, l='MpServer', x=-166.50, y=43.00, z=6.31], ug['Creeper'/10, l='MpServer', x=-167.50, y=43.00, z=9.50], us['Skeleton'/11, l='MpServer', x=-162.50, y=42.00, z=4.31], us['Skeleton'/12, l='MpServer', x=-167.50, y=43.00, z=6.50], ux['Zombie'/13, l='MpServer', x=-168.38, y=54.00, z=4.97], sx['Pig'/14, l='MpServer', x=-174.50, y=107.00, z=3.50], ug['Creeper'/15, l='MpServer', x=-168.47, y=32.00, z=72.97], tb['Squid'/16, l='MpServer', x=-149.50, y=60.38, z=-48.69], sn['Bat'/19, l='MpServer', x=-158.50, y=13.85, z=-24.94], sn['Bat'/21, l='MpServer', x=-156.81, y=51.64, z=-40.78], sn['Bat'/20, l='MpServer', x=-169.75, y=48.11, z=-51.25], sq['Cow'/22, l='MpServer', x=-153.72, y=106.00, z=-39.56], sq['Cow'/25, l='MpServer', x=-156.50, y=121.00, z=-24.50], sx['Pig'/27, l='MpServer', x=-156.47, y=89.00, z=-6.66], sx['Pig'/26, l='MpServer', x=-157.06, y=73.00, z=-0.88], us['Skeleton'/29, l='MpServer', x=-156.50, y=58.00, z=4.50], sx['Pig'/28, l='MpServer', x=-152.72, y=105.00, z=-7.06], sn['Bat'/31, l='MpServer', x=-139.44, y=55.39, z=-3.13], pd['entity.LeashKnot.name'/268, l='MpServer', x=-125.50, y=119.50, z=9.50], us['Skeleton'/30, l='MpServer', x=-156.50, y=58.00, z=3.50], pd['entity.LeashKnot.name'/269, l='MpServer', x=-125.50, y=119.50, z=15.50], us['Skeleton'/34, l='MpServer', x=-152.50, y=19.00, z=66.50], us['Skeleton'/35, l='MpServer', x=-152.50, y=19.00, z=64.50], sn['Bat'/518, l='MpServer', x=-38.27, y=47.67, z=33.51], sx['Pig'/32, l='MpServer', x=-153.78, y=74.00, z=0.81], sn['Bat'/519, l='MpServer', x=-38.44, y=49.00, z=32.22], ux['Zombie'/33, l='MpServer', x=-151.50, y=19.00, z=66.50], ug['Creeper'/38, l='MpServer', x=-147.00, y=63.00, z=-61.59], us['Skeleton'/36, l='MpServer', x=-152.50, y=19.00, z=67.50], ux['Zombie'/42, l='MpServer', x=-140.66, y=94.00, z=-10.44], pk['Painting'/43, l='MpServer', x=-128.94, y=107.50, z=-2.50], ux['Zombie'/40, l='MpServer', x=-134.84, y=79.00, z=-52.50], ux['Zombie'/41, l='MpServer', x=-136.59, y=110.00, z=-20.03], ug['Creeper'/46, l='MpServer', x=-114.50, y=38.00, z=-57.50], ug['Creeper'/47, l='MpServer', x=-113.97, y=36.00, z=-53.50], pk['Painting'/44, l='MpServer', x=-135.00, y=108.00, z=-0.06], ug['Creeper'/45, l='MpServer', x=-113.50, y=38.00, z=-55.50], bgh['Skycrafter231'/270, l='MpServer', x=-117.30, y=120.62, z=6.40], us['Skeleton'/51, l='MpServer', x=-113.17, y=74.00, z=-52.50], ux['Zombie'/50, l='MpServer', x=-127.72, y=80.00, z=-53.97], ug['Creeper'/49, l='MpServer', x=-115.34, y=76.00, z=-55.50], ux['Zombie'/48, l='MpServer', x=-115.50, y=38.00, z=-59.50], ug['Creeper'/55, l='MpServer', x=-126.44, y=107.57, z=4.38], ux['Zombie'/54, l='MpServer', x=-129.06, y=99.00, z=-27.50], ug['Creeper'/53, l='MpServer', x=-118.50, y=84.00, z=-30.50], ug['Creeper'/52, l='MpServer', x=-123.34, y=88.00, z=-31.03], sr['Trolly'/59, l='MpServer', x=-123.28, y=119.00, z=16.16], vc['Villager'/58, l='MpServer', x=-119.50, y=119.00, z=4.50], vc['Villager'/57, l='MpServer', x=-118.50, y=119.00, z=7.50], sr['Star'/56, l='MpServer', x=-123.38, y=119.00, z=8.84], ug['Creeper'/63, l='MpServer', x=-105.44, y=19.00, z=-11.56], ug['Creeper'/62, l='MpServer', x=-111.56, y=13.00, z=-17.00], ux['Zombie'/61, l='MpServer', x=-115.50, y=72.00, z=77.50], ux['Zombie'/60, l='MpServer', x=-120.50, y=53.00, z=77.50], ux['Zombie'/68, l='MpServer', x=-102.50, y=28.00, z=26.50], ug['Creeper'/69, l='MpServer', x=-101.50, y=28.00, z=27.50], ux['Zombie'/70, l='MpServer', x=-100.59, y=59.00, z=26.00], ux['Zombie'/71, l='MpServer', x=-101.47, y=31.00, z=36.03], us['Skeleton'/64, l='MpServer', x=-99.50, y=21.00, z=-10.50], ug['Creeper'/65, l='MpServer', x=-108.09, y=30.00, z=-7.56], ug['Creeper'/66, l='MpServer', x=-102.34, y=26.00, z=-6.47], ut['Slime'/67, l='MpServer', x=-97.31, y=28.00, z=19.31], sq['Cow'/76, l='MpServer', x=-80.47, y=121.00, z=-30.34], sq['Cow'/77, l='MpServer', x=-86.69, y=80.00, z=11.34], sq['Cow'/78, l='MpServer', x=-93.53, y=97.00, z=8.25], us['Skeleton'/79, l='MpServer', x=-90.56, y=54.00, z=25.06], ux['Zombie'/72, l='MpServer', x=-104.50, y=20.00, z=40.50], ux['Zombie'/73, l='MpServer', x=-102.88, y=21.00, z=39.50], us['Skeleton'/345, l='MpServer', x=-113.50, y=36.00, z=-66.50], sn['Bat'/74, l='MpServer', x=-96.25, y=51.10, z=43.41], ug['Creeper'/75, l='MpServer', x=-89.38, y=17.00, z=-32.03], uh['Enderman'/85, l='MpServer', x=-89.34, y=44.00, z=61.00], us['Skeleton'/84, l='MpServer', x=-91.59, y=44.00, z=51.84], sn['Bat'/87, l='MpServer', x=-78.72, y=38.67, z=59.03], sn['Bat'/86, l='MpServer', x=-80.47, y=37.82, z=56.75], sn['Bat'/81, l='MpServer', x=-102.81, y=50.10, z=33.75], sn['Bat'/80, l='MpServer', x=-78.47, y=39.79, z=34.56], uh['Enderman'/83, l='MpServer', x=-91.50, y=44.00, z=59.50], ux['Zombie'/82, l='MpServer', x=-95.50, y=39.00, z=52.50], ug['Creeper'/93, l='MpServer', x=-70.41, y=59.44, z=26.63], tb['Squid'/92, l='MpServer', x=-66.06, y=59.28, z=33.44], sq['Cow'/95, l='MpServer', x=-69.22, y=86.00, z=57.19], uu['Spider'/94, l='MpServer', x=-79.97, y=52.00, z=46.59], sq['Cow'/89, l='MpServer', x=-79.47, y=79.00, z=-10.50], sq['Cow'/88, l='MpServer', x=-78.69, y=125.00, z=-39.34], sn['Bat'/91, l='MpServer', x=-77.66, y=39.08, z=32.41], sq['Cow'/90, l='MpServer', x=-74.84, y=101.00, z=-0.16], sq['Cow'/102, l='MpServer', x=-59.47, y=91.00, z=-21.34], tb['Squid'/103, l='MpServer', x=-61.50, y=59.22, z=22.50], ug['Creeper'/100, l='MpServer', x=-54.03, y=36.00, z=-51.50], ux['Zombie'/101, l='MpServer', x=-49.66, y=56.00, z=-59.66], sq['Cow'/98, l='MpServer', x=-68.41, y=91.00, z=66.63], ug['Creeper'/99, l='MpServer', x=-52.50, y=36.00, z=-58.50], us['Skeleton'/96, l='MpServer', x=-76.50, y=50.00, z=75.50], sn['Bat'/97, l='MpServer', x=-72.59, y=50.98, z=78.47], ug['Creeper'/110, l='MpServer', x=-39.28, y=111.00, z=-45.50], ug['Creeper'/111, l='MpServer', x=-45.38, y=108.00, z=-61.41], sq['Cow'/106, l='MpServer', x=-61.66, y=89.00, z=63.41], ug['Creeper'/104, l='MpServer', x=-58.50, y=31.00, z=49.50], sq['Cow'/105, l='MpServer', x=-51.47, y=86.00, z=60.66], sn['Bat'/116, l='MpServer', x=-49.09, y=54.82, z=65.31], ux['Zombie'/366, l='MpServer', x=-60.59, y=100.00, z=-66.00], ux['Zombie'/367, l='MpServer', x=-56.91, y=100.00, z=-67.50], pk['Painting'/43, l='MpServer', x=-128.94, y=107.50, z=-2.50], pk['Painting'/44, l='MpServer', x=-135.00, y=108.00, z=-0.06], tt['item.item.beefRaw'/501, l='MpServer', x=-154.22, y=68.13, z=-40.00]]
	Retry entities: 0 total; []
	Server brand: vanilla
	Server type: Integrated singleplayer server
Stacktrace:
	at bgc.a(SourceFile:297)
	at awp.b(SourceFile:1874)
	at awp.e(SourceFile:686)
	at net.minecraft.client.main.Main.main(SourceFile:104)

-- System Details --
Details:
	Minecraft Version: 13w38c
	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, sharing), Oracle Corporation
	Memory: 107315176 bytes (102 MB) / 333328384 bytes (317 MB) up to 518979584 bytes (494 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
	AABB Pool Size: 11029 (617624 bytes; 0 MB) allocated, 4 (224 bytes; 0 MB) used
	IntCache: cache: 7, tcache: 0, allocated: 13, tallocated: 95
	Launched Version: 13w38c
	LWJGL: 2.9.0
	OpenGL: Intel(R) HD Graphics 3000 GL version 3.1.0 - Build 9.17.10.2828, Intel
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Packs: [JohnSmithLegacy_2.zip]
	Current Language: English (US)
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 2638 (147728 bytes; 0 MB) allocated, 27 (1512 bytes; 0 MB) used

You can see this full report at http://hopper.minecraft.net/crashes/minecraft/MCX-198069/12786108/