Upon loading my world the game crashes with the following report:

---- Minecraft Crash Report ----
// This doesn't make any sense!

Time: 8/16/15 1:57 PM
Description: Executing command block

java.lang.NullPointerException: Executing command block
at acj.a(SourceFile:380)
at xc.e_(SourceFile:309)
at o$11.a(SourceFile:321)
at o$11.apply(SourceFile:318)
at com.google.common.base.Predicates$AndPredicate.apply(Predicates.java:359)
at com.google.common.base.Predicates$AndPredicate.apply(Predicates.java:359)
at agh.a(SourceFile:2248)
at o.a(SourceFile:454)
at o.b(SourceFile:138)
at j.a(SourceFile:49)
at afx.a(SourceFile:98)
at aiv.b(SourceFile:56)
at lk.a(SourceFile:529)
at lk.d(SourceFile:201)
at net.minecraft.server.MinecraftServer.D(SourceFile:617)
at net.minecraft.server.MinecraftServer.C(SourceFile:553)
at buj.C(SourceFile:152)
at net.minecraft.server.MinecraftServer.run(SourceFile:457)
at java.lang.Thread.run(Unknown Source)

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

– Head –
Stacktrace:
at acj.a(SourceFile:380)
at xc.e_(SourceFile:309)
at o$11.a(SourceFile:321)
at o$11.apply(SourceFile:318)
at com.google.common.base.Predicates$AndPredicate.apply(Predicates.java:359)
at com.google.common.base.Predicates$AndPredicate.apply(Predicates.java:359)
at agh.a(SourceFile:2248)
at o.a(SourceFile:454)
at o.b(SourceFile:138)
at j.a(SourceFile:49)

– Command to be executed –
Details:
Command: /testfor @e[name=HARBORMAN]
Name: @
Stacktrace:
at afx.a(SourceFile:98)
at aiv.b(SourceFile:56)

– Block being ticked –
Details:
Block: minecraft:command_block[triggered=true]
Block location: World: (170,59,-199), Chunk: (at 10,3,9 in 10,-13; contains blocks 160,0,-208 to 175,255,-193), Region: (0,-1; contains chunks 0,-32 to 31,-1, blocks 0,0,-512 to 511,255,-1)
Stacktrace:
at lk.a(SourceFile:529)
at lk.d(SourceFile:201)

– Affected level –
Details:
Level name: Chi-Chitopia Prime
All players: 1 total; [ll['Vahkiti'/767, l='Chi-Chitopia Prime', x=174.70, y=71.00, z=59.70]]
Chunk stats: ServerChunkCache: 1101 Drop: 0
Level seed: -571656288452352023
Level generator: ID 00 - default, ver 1. Features enabled: true
Level generator options:
Level spawn location: 141.00,69.00,149.00 - World: (141,69,149), Chunk: (at 13,4,5 in 8,9; contains blocks 128,0,144 to 143,255,159), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Level time: 219602362 game time, 1277276 day time
Level dimension: 0
Level storage version: 0x04ABD - Anvil
Level weather: Rain time: 13026 (now: true), thunder time: 11797 (now: false)
Level game mode: Game mode: adventure (ID 2). Hardcore: false. Cheats: true
Stacktrace:
at net.minecraft.server.MinecraftServer.D(SourceFile:617)
at net.minecraft.server.MinecraftServer.C(SourceFile:553)
at buj.C(SourceFile:152)
at net.minecraft.server.MinecraftServer.run(SourceFile:457)
at java.lang.Thread.run(Unknown Source)

– System Details –
Details:
Minecraft Version: 15w33c
Operating System: Windows 8.1 (amd64) version 6.3
Java Version: 1.8.0_40, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 224814960 bytes (214 MB) / 557166592 bytes (531 MB) up to 1060372480 bytes (1011 MB)
JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
IntCache: cache: 0, tcache: 0, allocated: 12, tallocated: 94
Profiler Position: N/A (disabled)
Player Count: 1 / 8; [ll['Vahkiti'/767, l='Chi-Chitopia Prime', x=174.70, y=71.00, z=59.70]]
Type: Integrated Server (map_client.txt)
Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.

This only seems to occur on the latest snapshot, (15w33c) and not on the previous. In addition, running the same map on a server will cause the player to be kicked with the following error:

Internal Exception: io.netty.handler.codec.DecoderException: com.google.gson.JsonSyntaxException: com.google.gsonMalformedJsonException: Use JsonReader.setLenient(true) to accept malformed JSON at line 1 column 1