Server Error Report

While testing the Development Environment I played a litte game against a bot.
(I used two Star Wars Commander Decks)

Game exception occurred: java.util.ConcurrentModificationException
Server version: 1.4.50-V2 (build: runtime)
java.util.ArrayList$Itr.checkForComodification(ArrayList.java:911)
java.util.ArrayList$Itr.next(ArrayList.java:861)
mage.player.ai.MCTSNode.merge(MCTSNode.java:392)
mage.player.ai.MCTSNode.merge(MCTSNode.java:402)
mage.player.ai.ComputerPlayerMCTS.applyMCTS(ComputerPlayerMCTS.java:185)
mage.player.ai.ComputerPlayerMCTS.calculateActions(ComputerPlayerMCTS.java:96)
mage.player.ai.ComputerPlayerMCTS.getNextAction(ComputerPlayerMCTS.java:111)
mage.player.ai.ComputerPlayerMCTS.priority(ComputerPlayerMCTS.java:77)
mage.game.GameImpl.playPriority(GameImpl.java:1540)
mage.game.turn.Step.priority(Step.java:61)
mage.game.turn.Phase.playStep(Phase.java:184)
mage.game.turn.Phase.play(Phase.java:89)
mage.game.turn.Turn.play(Turn.java:132)
mage.game.GameImpl.playTurn(GameImpl.java:1056)
mage.game.GameImpl.play(GameImpl.java:966)
mage.game.GameImpl.start(GameImpl.java:942)
mage.server.game.GameWorker.call(GameWorker.java:34)
java.util.concurrent.FutureTask.run(FutureTask.java:266)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
java.lang.Thread.run(Thread.java:750)