Game crashing

Minecraft Crash Report ----
// I just don't know what went wrong 😞

Time: 12/7/15 3:12 PM
Description: Ticking entity

java.lang.NullPointerException: Ticking entity
at aaa.a(SourceFile:44)
at zu.m(SourceFile:117)
at ahn.a(SourceFile:1467)
at lp.a(SourceFile:719)
at ahn.g(SourceFile:1445)
at ahn.k(SourceFile:1335)
at lp.k(SourceFile:552)
at net.minecraft.server.MinecraftServer.D(SourceFile:625)
at net.minecraft.server.MinecraftServer.C(SourceFile:553)
at bxz.C(SourceFile:154)
at net.minecraft.server.MinecraftServer.run(SourceFile:457)
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 –
Stacktrace:
at aaa.a(SourceFile:44)
at zu.m(SourceFile:117)
at ahn.a(SourceFile:1467)
at lp.a(SourceFile:719)
at ahn.g(SourceFile:1445)

– Entity being ticked –
Details:
Entity Type: SmallFireball (aaa)
Entity ID: 254
Entity Name: Small Fireball
Entity's Exact location: 126.73, 67.27, 337.50
Entity's Block location: World: (126,67,337), Chunk: (at 14,4,1 in 7,21; contains blocks 112,0,336 to 127,255,351), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Entity's Momentum: 0.17, -0.16, 1.04
Entity's Passengers: []
Entity's Vehicle: ~_ERROR~ NullPointerException: null
Stacktrace:
at ahn.k(SourceFile:1335)
at lp.k(SourceFile:552)

– Affected level –
Details:
Level name: Castle
All players: 1 total; [lr['gingervitis1531'/214, l='Castle', x=125.57, y=67.00, z=335.82]]
Chunk stats: ServerChunkCache: 629 Drop: 0
Level seed: -1801421346
Level generator: ID 00 - default, ver 1. Features enabled: false
Level generator options:
Level spawn location: World: (0,0,0), Chunk: (at 0,0,0 in 0,0; contains blocks 0,0,0 to 15,255,15), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Level time: 0 game time, 0 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: ~_ERROR~ NullPointerException: null
Stacktrace:
at net.minecraft.server.MinecraftServer.D(SourceFile:625)
at net.minecraft.server.MinecraftServer.C(SourceFile:553)
at bxz.C(SourceFile:154)
at net.minecraft.server.MinecraftServer.run(SourceFile:457)
at java.lang.Thread.run(Thread.java:745)

– System Details –
Details:
Minecraft Version: 15w49b
Operating System: Mac OS X (x86_64) version 10.10.3
Java Version: 1.8.0_60, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 143371240 bytes (136 MB) / 358723584 bytes (342 MB) up to 1060372480 bytes (1011 MB)
JVM Flags: 5 total; -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; [lr['gingervitis1531'/214, l='Castle', x=125.57, y=67.00, z=335.82]]
Type: Integrated Server (map_client.txt)
Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.