---- Minecraft Crash Report ----
// My bad.

Time: 6/4/17 11:41 AM
Description: Exception ticking world

java.util.ConcurrentModificationException
	at java.util.HashMap$HashIterator.remove(HashMap.java:1443)
	at ol.d(SourceFile:198)
	at om.d(SourceFile:205)
	at net.minecraft.server.MinecraftServer.D(SourceFile:624)
	at net.minecraft.server.MinecraftServer.C(SourceFile:560)
	at chb.C(SourceFile:154)
	at net.minecraft.server.MinecraftServer.run(SourceFile:464)
	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 java.util.HashMap$HashIterator.remove(HashMap.java:1443)
	at ol.d(SourceFile:198)
	at om.d(SourceFile:205)

-- Affected level --
Details:
	Level name: Debug World
	All players: 0 total; []
	Chunk stats: ServerChunkCache: 548 Drop: 294
	Level seed: 0
	Level generator: ID 05 - debug_all_block_states, ver 0. Features enabled: false
	Level generator options: 
	Level spawn location: World: (0,1,0), 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: 138962 game time, 6000 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: spectator (ID 3). Hardcore: false. Cheats: true
Stacktrace:
	at net.minecraft.server.MinecraftServer.D(SourceFile:624)
	at net.minecraft.server.MinecraftServer.C(SourceFile:560)
	at chb.C(SourceFile:154)
	at net.minecraft.server.MinecraftServer.run(SourceFile:464)
	at java.lang.Thread.run(Thread.java:745)

-- System Details --
Details:
	Minecraft Version: 1.12-pre7
	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: 168437360 bytes (160 MB) / 321634304 bytes (306 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: 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.