ConcurrentModificationException

java.util.ConcurrentModificationException
  at java.util.ArrayList$ArrayListSpliterator.tryAdvance(Unknown Source)
  at java.util.stream.ReferencePipeline.forEachWithCancel(Unknown Source)
  at java.util.stream.AbstractPipeline.copyIntoWithCancel(Unknown Source)
  at java.util.stream.AbstractPipeline.copyInto(Unknown Source)
  at java.util.stream.AbstractPipeline.wrapAndCopyInto(Unknown Source)
  at java.util.stream.FindOps$FindOp.evaluateSequential(Unknown Source)
  at java.util.stream.AbstractPipeline.evaluate(Unknown Source)
  at java.util.stream.ReferencePipeline.findAny(Unknown Source)
  at sx.blah.discord.handle.impl.obj.Guild.getUserByID(Guild.java:184)
  at sx.blah.discord.api.internal.DiscordClientImpl.getUserByID(DiscordClientImpl.java:399)
  at sx.blah.discord.api.internal.DiscordUtils.getPrivateChannelFromJSON(DiscordUtils.java:323)
  at sx.blah.discord.api.internal.DiscordClientImpl.getOrCreatePMChannel(DiscordClientImpl.java:427)
  at io.github.loldatsec.moobot.managers.MessageManager.sendPrivateMessage(MessageManager.java:135)
  at io.github.loldatsec.moobot.managers.InputEventManager.sendHelp(InputEventManager.java:73)
  at io.github.loldatsec.moobot.managers.InputEventManager.access$000(InputEventManager.java:19)
  at io.github.loldatsec.moobot.managers.InputEventManager$1.run(InputEventManager.java:41)