---- Minecraft Crash Report ----
// Don't be sad. I'll do better next time, I promise!

Time: 04/03/18 15:06
Description: Exception ticking world

java.util.ConcurrentModificationException
        at java.util.HashMap$HashIterator.remove(HashMap.java:1456)
        at on.d(SourceFile:198)
        at oo.d(SourceFile:206)
        at net.minecraft.server.MinecraftServer.D(SourceFile:624)
        at nz.D(SourceFile:349)
        at net.minecraft.server.MinecraftServer.C(SourceFile:560)
        at net.minecraft.server.MinecraftServer.run(SourceFile:464)
        at java.lang.Thread.run(Thread.java:748)


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:1456)
        at on.d(SourceFile:198)
        at oo.d(SourceFile:206)

-- Affected level --
Details:
        Level name: world
        All players: 0 total; []
        Chunk stats: ServerChunkCache: 367 Drop: 96
        Level seed: -8814260235774519579
        Level generator: ID 00 - default, ver 1. Features enabled: true
        Level generator options:
        Level spawn location: World: (40,64,256), Chunk: (at 8,4,0 in 2,16; contains blocks 32,0,256 to 47,255,271), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
        Level time: 35973883 game time, 36460641 day time
        Level dimension: 0
        Level storage version: 0x04ABD - Anvil
        Level weather: Rain time: 171620 (now: false), thunder time: 90991 (now: false)
        Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: false
Stacktrace:
        at net.minecraft.server.MinecraftServer.D(SourceFile:624)
        at nz.D(SourceFile:349)
        at net.minecraft.server.MinecraftServer.C(SourceFile:560)
        at net.minecraft.server.MinecraftServer.run(SourceFile:464)
        at java.lang.Thread.run(Thread.java:748)

-- System Details --
Details:
        Minecraft Version: 1.12.2
        Operating System: Linux (amd64) version 4.4.0-104-generic
        Java Version: 1.8.0_151, Oracle Corporation
        Java VM Version: OpenJDK 64-Bit Server VM (mixed mode), Oracle Corporation
        Memory: 862496760 bytes (822 MB) / 1037959168 bytes (989 MB) up to 1037959168 bytes (989 MB)
        JVM Flags: 2 total; -Xmx1024M -Xms1024M
        IntCache: cache: 0, tcache: 0, allocated: 12, tallocated: 94
        Profiler Position: N/A (disabled)
        Player Count: 0 / 20; []
        Is Modded: Unknown (can't tell)
        Type: Dedicated Server (map_server.txt)