java.util.concurrent.ExecutionException: java.lang.UnsupportedOperationException
	at java.util.concurrent.FutureTask.report(FutureTask.java:122) ~[?:1.8.0_212]
	at java.util.concurrent.FutureTask.get(FutureTask.java:192) ~[?:1.8.0_212]
	at net.minecraft.util.Util.func_181617_a(SourceFile:47) [h.class:?]
	at org.spongepowered.common.SpongeImplHooks.onUtilRunTask(SpongeImplHooks.java:307) [SpongeImplHooks.class:1.12.2-2825-7.1.6]
	at net.minecraft.server.MinecraftServer.redirect$onRun$zjo000(MinecraftServer.java:3970) [MinecraftServer.class:?]
	at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:723) [MinecraftServer.class:?]
	at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:397) [nz.class:?]
	at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:668) [MinecraftServer.class:?]
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:526) [MinecraftServer.class:?]
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_212]
Caused by: java.lang.UnsupportedOperationException
	at java.util.concurrent.CopyOnWriteArrayList$COWIterator.remove(CopyOnWriteArrayList.java:1178) ~[?:1.8.0_212]
	at de.waterdu.aquagyms.gym.queue.Queue.cancelChallenges(Queue.java:127) ~[Queue.class:?]
	at de.waterdu.aquagyms.ui.pages.players.gym.TeamSelectionUI.onButtonClick(TeamSelectionUI.java:195) ~[TeamSelectionUI.class:?]
	at de.waterdu.aquagyms.ui.internal.AquaUIContainer.func_184996_a(AquaUIContainer.java:62) ~[AquaUIContainer.class:?]
	at net.minecraft.network.NetHandlerPlayServer.func_147351_a(NetHandlerPlayServer.java:1162) ~[pa.class:?]
	at net.minecraft.network.play.client.CPacketClickWindow.func_148833_a(CPacketClickWindow.java:38) ~[lf.class:?]
	at net.minecraft.network.play.client.CPacketClickWindow.func_148833_a(CPacketClickWindow.java:12) ~[lf.class:?]
	at org.spongepowered.common.event.tracking.phase.packet.PacketPhaseUtil.onProcessPacket(PacketPhaseUtil.java:193) ~[PacketPhaseUtil.class:1.12.2-2825-7.1.6]
	at net.minecraft.network.PacketThreadUtil$1.redirect$onProcessPacket$zlk000(SourceFile:539) ~[hv$1.class:?]
	at net.minecraft.network.PacketThreadUtil$1.run(SourceFile:13) ~[hv$1.class:?]
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) ~[?:1.8.0_212]
	at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[?:1.8.0_212]
	at net.minecraft.util.Util.func_181617_a(SourceFile:46) ~[h.class:?]
	... 7 more
[10:56:16] [Server thread/INFO] [nucleus]: Menacejam ran the command: /l Gg good sir, that was a good battle ahaha
[10:56:16] [Server thread/INFO] [net.minecraft.server.dedicated.DedicatedServer]: [Local] Creamlord Menacejam: Gg good sir, that was a good battle ahaha
[10:56:17] [Server thread/FATAL] [net.minecraft.server.MinecraftServer]: Error executing task
java.util.concurrent.ExecutionException: java.lang.UnsupportedOperationException
	at java.util.concurrent.FutureTask.report(FutureTask.java:122) ~[?:1.8.0_212]
	at java.util.concurrent.FutureTask.get(FutureTask.java:192) ~[?:1.8.0_212]
	at net.minecraft.util.Util.func_181617_a(SourceFile:47) [h.class:?]
	at org.spongepowered.common.SpongeImplHooks.onUtilRunTask(SpongeImplHooks.java:307) [SpongeImplHooks.class:1.12.2-2825-7.1.6]
	at net.minecraft.server.MinecraftServer.redirect$onRun$zjo000(MinecraftServer.java:3970) [MinecraftServer.class:?]
	at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:723) [MinecraftServer.class:?]
	at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:397) [nz.class:?]
	at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:668) [MinecraftServer.class:?]
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:526) [MinecraftServer.class:?]
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_212]
Caused by: java.lang.UnsupportedOperationException
	at java.util.concurrent.CopyOnWriteArrayList$COWIterator.remove(CopyOnWriteArrayList.java:1178) ~[?:1.8.0_212]
	at de.waterdu.aquagyms.gym.queue.Queue.cancelChallenges(Queue.java:127) ~[Queue.class:?]
	at de.waterdu.aquagyms.ui.pages.players.gym.TeamSelectionUI.onButtonClick(TeamSelectionUI.java:195) ~[TeamSelectionUI.class:?]
	at de.waterdu.aquagyms.ui.internal.AquaUIContainer.func_184996_a(AquaUIContainer.java:62) ~[AquaUIContainer.class:?]
	at net.minecraft.network.NetHandlerPlayServer.func_147351_a(NetHandlerPlayServer.java:1162) ~[pa.class:?]
	at net.minecraft.network.play.client.CPacketClickWindow.func_148833_a(CPacketClickWindow.java:38) ~[lf.class:?]
	at net.minecraft.network.play.client.CPacketClickWindow.func_148833_a(CPacketClickWindow.java:12) ~[lf.class:?]
	at org.spongepowered.common.event.tracking.phase.packet.PacketPhaseUtil.onProcessPacket(PacketPhaseUtil.java:193) ~[PacketPhaseUtil.class:1.12.2-2825-7.1.6]
	at net.minecraft.network.PacketThreadUtil$1.redirect$onProcessPacket$zlk000(SourceFile:539) ~[hv$1.class:?]
	at net.minecraft.network.PacketThreadUtil$1.run(SourceFile:13) ~[hv$1.class:?]
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) ~[?:1.8.0_212]
	at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[?:1.8.0_212]
	at net.minecraft.util.Util.func_181617_a(SourceFile:46) ~[h.class:?]
	... 7 more