Game crashes suddenly.
Crash report:
---- Minecraft Crash Report ----
// Oops.

Time: 2-12-15 19:12
Description: Exception ticking world

java.lang.IllegalArgumentException: Cannot get property arh

{name=half, clazz=class als$a, values=[top, bottom]}

as it does not exist in aqv

{block=minecraft:double_wooden_slab, properties=[variant]}

at aqv$a.c(SourceFile:165)
at als.k(SourceFile:50)
at aqv$a.q(SourceFile:388)
at ahu.a(SourceFile:203)
at ahu.a(SourceFile:132)
at lp.d(SourceFile:198)
at net.minecraft.server.MinecraftServer.D(SourceFile:617)
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(Unknown Source)

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

– Head –
Stacktrace:
at aqv$a.c(SourceFile:165)
at als.k(SourceFile:50)
at aqv$a.q(SourceFile:388)
at ahu.a(SourceFile:203)
at ahu.a(SourceFile:132)
at lp.d(SourceFile:198)

– Affected level –
Details:
Level name: World
All players: 1 total; [lr['TheRealKS'/213, l='World', x=-184,34, y=63,00, z=331,52]]
Chunk stats: ServerChunkCache: 647 Drop: 0
Level seed: -3999488446484685207
Level generator: ID 00 - default, ver 1. Features enabled: true
Level generator options:
Level spawn location: World: (-196,64,248), Chunk: (at 12,4,8 in -13,15; contains blocks -208,0,240 to -193,255,255), Region: (-1,0; contains chunks -32,0 to -1,31, blocks -512,0,0 to -1,255,511)
Level time: 8127153 game time, 12568 day time
Level dimension: 0
Level storage version: 0x04ABD - Anvil
Level weather: Rain time: 128891 (now: false), thunder time: 196 (now: false)
Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: true
Stacktrace:
at net.minecraft.server.MinecraftServer.D(SourceFile:617)
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(Unknown Source)

– System Details –
Details:
Minecraft Version: 15w49a
Operating System: Windows 10 (amd64) version 10.0
Java Version: 1.8.0_65, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 286148328 bytes (272 MB) / 631824384 bytes (602 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; [lr['TheRealKS'/213, l='World', x=-184,34, y=63,00, z=331,52]]
Type: Integrated Server (map_client.txt)
Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.