Using a fishing rod whilst rapidly teleporting in tiny intervals and given the levitation effect at level 255 causes instant crashes for me.

---- Minecraft Crash Report ----
// Hi. I'm Minecraft, and I'm a crashaholic.

Time: 31/05/16 22:09
Description: Executing command block

java.lang.NullPointerException: Executing command block
at rx.a(SourceFile:324)
at p$1.a(SourceFile:188)
at p$1.apply(SourceFile:185)
at com.google.common.base.Predicates$AndPredicate.apply(Predicates.java:359)
at com.google.common.base.Predicates$AndPredicate.apply(Predicates.java:359)
at aic.a(SourceFile:2283)
at p.a(SourceFile:490)
at p.b(SourceFile:143)
at k.a(SourceFile:51)
at ahr.a(SourceFile:114)
at akw.b(SourceFile:96)
at lr.a(SourceFile:645)
at lr.d(SourceFile:216)
at net.minecraft.server.MinecraftServer.D(SourceFile:618)
at net.minecraft.server.MinecraftServer.C(SourceFile:554)
at bzk.C(SourceFile:155)
at net.minecraft.server.MinecraftServer.run(SourceFile:458)
at java.lang.Thread.run(Thread.java:745)

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

– Head –
Thread: Server thread
Stacktrace:
at rx.a(SourceFile:324)
at p$1.a(SourceFile:188)
at p$1.apply(SourceFile:185)
at com.google.common.base.Predicates$AndPredicate.apply(Predicates.java:359)
at com.google.common.base.Predicates$AndPredicate.apply(Predicates.java:359)
at aic.a(SourceFile:2283)
at p.a(SourceFile:490)
at p.b(SourceFile:143)
at k.a(SourceFile:51)

– Command to be executed –
Details:
Command: /scoreboard players set @e[type=Item] c_1 2 {Item:{id:minecraft:stone_pickaxe}}
Name: @
Stacktrace:
at ahr.a(SourceFile:114)
at akw.b(SourceFile:96)

– Block being ticked –
Details:
Block: minecraft:repeating_command_block[conditional=false,facing=up]
Block location: World: (159,4,701), Chunk: (at 15,0,13 in 9,43; contains blocks 144,0,688 to 159,255,703), Region: (0,1; contains chunks 0,32 to 31,63, blocks 0,0,512 to 511,255,1023)
Stacktrace:
at lr.a(SourceFile:645)
at lr.d(SourceFile:216)

– Affected level –
Details:
Level name: Omniverse Core
All players: 1 total; [lt['Valinax'/194, l='Omniverse Core', x=221.66, y=4.57, z=652.40]]
Chunk stats: ServerChunkCache: 438 Drop: 0
Level seed: 6136438843060546068
Level generator: ID 01 - flat, ver 0. Features enabled: true
Level generator options:
Level spawn location: World: (148,4,740), Chunk: (at 4,0,4 in 9,46; contains blocks 144,0,736 to 159,255,751), Region: (0,1; contains chunks 0,32 to 31,63, blocks 0,0,512 to 511,255,1023)
Level time: 5927130 game time, 623784 day time
Level dimension: 0
Level storage version: 0x04ABD - Anvil
Level weather: Rain time: 1 (now: false), thunder time: 1 (now: false)
Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: true
Stacktrace:
at net.minecraft.server.MinecraftServer.D(SourceFile:618)
at net.minecraft.server.MinecraftServer.C(SourceFile:554)
at bzk.C(SourceFile:155)
at net.minecraft.server.MinecraftServer.run(SourceFile:458)
at java.lang.Thread.run(Thread.java:745)

– System Details –
Details:
Minecraft Version: 16w21b
Operating System: Windows 10 (amd64) version 10.0
Java Version: 1.8.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 153804936 bytes (146 MB) / 288096256 bytes (274 MB) up to 8576565248 bytes (8179 MB)
JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx8G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
Profiler Position: N/A (disabled)
Player Count: 1 / 8; [lt['Valinax'/194, l='Omniverse Core', x=221.66, y=4.57, z=652.40]]
Type: Integrated Server (map_client.txt)
Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.