it crashed when i was trading with a villager.

I expected to finish a trade with a villager in a super flat world in snapshot 13w41b then it crashed and it would not let me send an error report because it thought it was modded. i also had 3 command blocks set to teleport me.

here is the error report.

A detailed walkthrough of the error, its code path and all known details is as follows:
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– Head –
Stacktrace:
at java.util.ArrayList.rangeCheck(Unknown Source)
at java.util.ArrayList.get(Unknown Source)
at bdn.a(SourceFile:108)
at bcp.a(SourceFile:78)
at bdn.a(SourceFile:122)

– Screen render details –
Details:
Screen name: bdn
Mouse location: Scaled: (279, 72). Absolute: (837, 531)
Screen size: Scaled: (427, 250). Absolute: (1280, 750). Scale factor of 3

– Affected level –
Details:
Level name: MpServer
All players: 1 total; [bil['jaybeezee720'/125, l='MpServer', x=13.69, y=6.62, z=89.75]]
Chunk stats: MultiplayerChunkCache: 225, 225
Level seed: 0
Level generator: ID 00 - default, ver 1. Features enabled: false
Level generator options:
Level spawn location: World: (-40,4,-347), Chunk: (at 8,0,5 in -3,-22; contains blocks -48,0,-352 to -33,255,-337), Region: (-1,-1; contains chunks -32,-32 to -1,-1, blocks -512,0,-512 to -1,255,-1)
Level time: 37676 game time, 37676 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: 37 total; [bil['jaybeezee720'/125, l='MpServer', x=13.69, y=6.62, z=89.75], wy['Villager'/129, l='MpServer', x=-1.38, y=5.00, z=60.25], wy['Villager'/128, l='MpServer', x=-17.53, y=5.00, z=60.16], wy['Villager'/131, l='MpServer', x=-34.63, y=6.00, z=69.44], wy['Villager'/130, l='MpServer', x=9.56, y=5.00, z=78.84], uh['Bat'/306749, l='MpServer', x=-10.50, y=8.10, z=80.75], wy['Villager'/133, l='MpServer', x=8.57, y=5.00, z=69.57], wy['Villager'/132, l='MpServer', x=1.03, y=5.00, z=74.31], wy['Villager'/135, l='MpServer', x=2.50, y=5.00, z=59.69], wy['Villager'/134, l='MpServer', x=-18.69, y=5.00, z=59.88], uh['Bat'/302721, l='MpServer', x=-8.25, y=5.95, z=73.25], uh['Bat'/302724, l='MpServer', x=-13.19, y=6.02, z=75.41], uh['Bat'/358460, l='MpServer', x=-22.81, y=6.82, z=89.41], uh['Bat'/302725, l='MpServer', x=-9.59, y=5.73, z=73.25], uh['Bat'/308832, l='MpServer', x=1.75, y=5.05, z=64.75], wy['Villager'/110, l='MpServer', x=-0.28, y=5.00, z=74.31], wy['Villager'/111, l='MpServer', x=7.30, y=5.00, z=68.30], uh['Bat'/346781, l='MpServer', x=-7.81, y=6.00, z=80.75], uh['Bat'/300355, l='MpServer', x=2.19, y=6.10, z=62.75], wy['Villager'/119, l='MpServer', x=-34.31, y=6.00, z=70.29], wy['Villager'/118, l='MpServer', x=-26.35, y=5.00, z=66.28], wy['Villager'/117, l='MpServer', x=8.25, y=5.00, z=91.50], uh['Bat'/289072, l='MpServer', x=-22.81, y=7.10, z=89.66], wy['Villager'/116, l='MpServer', x=-13.63, y=5.00, z=80.94], wy['Villager'/115, l='MpServer', x=1.47, y=5.00, z=89.93], wy['Villager'/114, l='MpServer', x=9.31, y=5.00, z=80.53], wy['Villager'/113, l='MpServer', x=0.34, y=5.00, z=89.31], wy['Villager'/112, l='MpServer', x=13.41, y=5.00, z=87.84], wy['Villager'/127, l='MpServer', x=2.50, y=5.00, z=59.31], wy['Villager'/126, l='MpServer', x=-19.88, y=5.00, z=52.50], uh['Bat'/259595, l='MpServer', x=0.75, y=8.10, z=63.75], wy['Villager'/124, l='MpServer', x=-29.50, y=5.00, z=66.50], uh['Bat'/359744, l='MpServer', x=-26.84, y=7.98, z=88.25], wy['Villager'/123, l='MpServer', x=-25.84, y=5.00, z=88.78], wy['Villager'/122, l='MpServer', x=-27.39, y=5.00, z=67.03], wy['Villager'/121, l='MpServer', x=-27.27, y=5.00, z=66.31], wy['Villager'/120, l='MpServer', x=-14.28, y=5.00, z=79.56]]
Retry entities: 0 total; []
Server brand: vanilla
Server type: Integrated singleplayer server
Stacktrace:
at big.a(SourceFile:302)
at ayp.b(SourceFile:1935)