error

[19:53:32] [Server thread/INFO]: bobisawesomme issued server command: /msg Ben10142002 i cant talk
[19:53:41] [Server thread/INFO]: bobisawesomme issued server command: /msg Ben10142002 help
[19:53:57] [Server thread/INFO]: Ben10142002 issued server command: /msg bobisawesomme sigh, sure
[19:54:01] [Server thread/INFO]: bobisawesomme issued server command: /msg Ben10142002 i can only msg people
[19:54:15] [Server thread/INFO]: Death: bobisawesomme was slain by Zombie Pigman.
[19:54:16] [Server thread/INFO]: Ben10142002 issued server command: /msg bobisawesomme sigh, sure
[19:54:16] [Server thread/FATAL]: Error executing task
java.util.concurrent.ExecutionException: java.util.ConcurrentModificationException
	at java.util.concurrent.FutureTask.report(FutureTask.java:122) ~[?:1.8.0_45]
	at java.util.concurrent.FutureTask.get(FutureTask.java:192) ~[?:1.8.0_45]
	at net.minecraft.server.v1_8_R3.SystemUtils.a(SourceFile:61) [spigot.jar:git-Spigot-6a6b839-b0e81a4]
	at net.minecraft.server.v1_8_R3.MinecraftServer.B(MinecraftServer.java:718) [spigot.jar:git-Spigot-6a6b839-b0e81a4]
	at net.minecraft.server.v1_8_R3.DedicatedServer.B(DedicatedServer.java:367) [spigot.jar:git-Spigot-6a6b839-b0e81a4]
	at net.minecraft.server.v1_8_R3.MinecraftServer.A(MinecraftServer.java:657) [spigot.jar:git-Spigot-6a6b839-b0e81a4]
	at net.minecraft.server.v1_8_R3.MinecraftServer.run(MinecraftServer.java:560) [spigot.jar:git-Spigot-6a6b839-b0e81a4]
	at java.lang.Thread.run(Thread.java:745) [?:1.8.0_45]
Caused by: java.util.ConcurrentModificationException
	at java.util.HashMap$HashIterator.nextNode(HashMap.java:1429) ~[?:1.8.0_45]
	at java.util.HashMap$KeyIterator.next(HashMap.java:1453) ~[?:1.8.0_45]
	at net.minecraft.server.v1_8_R3.EntityTracker.track(EntityTracker.java:32) ~[spigot.jar:git-Spigot-6a6b839-b0e81a4]
	at net.minecraft.server.v1_8_R3.WorldManager.a(WorldManager.java:18) ~[spigot.jar:git-Spigot-6a6b839-b0e81a4]
	at net.minecraft.server.v1_8_R3.World.a(World.java:1066) ~[spigot.jar:git-Spigot-6a6b839-b0e81a4]
	at net.minecraft.server.v1_8_R3.WorldServer.a(WorldServer.java:973) ~[spigot.jar:git-Spigot-6a6b839-b0e81a4]
	at net.minecraft.server.v1_8_R3.World.addEntity(World.java:1059) ~[spigot.jar:git-Spigot-6a6b839-b0e81a4]
	at net.minecraft.server.v1_8_R3.World.addEntity(World.java:987) ~[spigot.jar:git-Spigot-6a6b839-b0e81a4]
	at net.minecraft.server.v1_8_R3.PlayerList.moveToWorld(PlayerList.java:604) ~[spigot.jar:git-Spigot-6a6b839-b0e81a4]
	at net.minecraft.server.v1_8_R3.PlayerList.moveToWorld(PlayerList.java:504) ~[spigot.jar:git-Spigot-6a6b839-b0e81a4]
	at net.minecraft.server.v1_8_R3.PlayerConnection.a(PlayerConnection.java:1366) ~[spigot.jar:git-Spigot-6a6b839-b0e81a4]
	at net.minecraft.server.v1_8_R3.PacketPlayInClientCommand.a(SourceFile:31) ~[spigot.jar:git-Spigot-6a6b839-b0e81a4]
	at net.minecraft.server.v1_8_R3.PacketPlayInClientCommand.a(SourceFile:8) ~[spigot.jar:git-Spigot-6a6b839-b0e81a4]
	at net.minecraft.server.v1_8_R3.PlayerConnectionUtils$1.run(SourceFile:13) ~[spigot.jar:git-Spigot-6a6b839-b0e81a4]
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) ~[?:1.8.0_45]
	at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[?:1.8.0_45]
	at net.minecraft.server.v1_8_R3.SystemUtils.a(SourceFile:60) ~[spigot.jar:git-Spigot-6a6b839-b0e81a4]
	... 5 more
[19:54:31] [Server thread/INFO]: bobisawesomme issued server command: /msg Ben10142002 whats happening
[19:54:57] [Server thread/INFO]: bobisawesomme issued server command: /msg Ben10142002 i didn't do anything
[19:54:57] [Server thread/WARN]: Ben10142002 moved too quickly! 282.9891874602763,5.0,396.0912821346329 (282.9891874602763, 5.0, 396.0912821346329)
[19:55:18] [User Authenticator #5/INFO]: [YourMC] Loaded data for player 'MC_Rainy'.
[19:55:18] [User Authenticator #5/INFO]: UUID of player MC_Rainy is 8cb4a167-4b17-48c6-bf17-97d18218da1e
[19:55:18] [Server thread/INFO]: MC_Rainy[/68.150.168.244:56992] logged in with entity id 25309 at ([world]2219.685629794629, 67.0, 1043.2386445579295)