Can't access world. Game crashed

I've tried to play my command block map but I getting this crash.

---- Minecraft Crash Report ----
// Shall we play a game?

Time: 4/5/17 9:15 PM
Description: Ticking memory connection

java.lang.NullPointerException: Ticking memory connection
	at mr.f(SourceFile:123)
	at mr.<init>(SourceFile:55)
	at om.h(SourceFile:910)
	at nr.<init>(SourceFile:168)
	at om.g(SourceFile:425)
	at od.b(SourceFile:120)
	at od.G_(SourceFile:66)
	at gd.a(SourceFile:231)
	at oa.c(SourceFile:187)
	at net.minecraft.server.MinecraftServer.D(SourceFile:652)
	at net.minecraft.server.MinecraftServer.C(SourceFile:562)
	at cfk.C(SourceFile:154)
	at net.minecraft.server.MinecraftServer.run(SourceFile:466)
	at java.lang.Thread.run(Unknown Source)


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

-- Head --
Thread: Server thread
Stacktrace:
	at mr.f(SourceFile:123)
	at mr.<init>(SourceFile:55)
	at om.h(SourceFile:910)
	at nr.<init>(SourceFile:168)
	at om.g(SourceFile:425)
	at od.b(SourceFile:120)
	at od.G_(SourceFile:66)
	at gd.a(SourceFile:231)

-- Ticking connection --
Details:
	Connection: gd@69b76f11
Stacktrace:
	at oa.c(SourceFile:187)
	at net.minecraft.server.MinecraftServer.D(SourceFile:652)
	at net.minecraft.server.MinecraftServer.C(SourceFile:562)
	at cfk.C(SourceFile:154)
	at net.minecraft.server.MinecraftServer.run(SourceFile:466)
	at java.lang.Thread.run(Unknown Source)

-- System Details --
Details:
	Minecraft Version: 17w14a
	Operating System: Windows 8.1 (amd64) version 6.3
	Java Version: 1.8.0_121, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 98894008 bytes (94 MB) / 229027840 bytes (218 MB) up to 2134114304 bytes (2035 MB)
	JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx2G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	Profiler Position: N/A (disabled)
	Player Count: 0 / 8; []
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.