Everytime i attack an NPC i get this error in console

Code:
at server.clip.region.Region.getClipping(Region.java:341)
	at server.model.players.PathFinder.findRoute(PathFinder.java:62)
	at server.model.players.PlayerAssistant.playerWalk(PlayerAssistant.java:4208)
	at server.model.players.PlayerAssistant.followNpc(PlayerAssistant.java:2407)
	at server.model.players.Player.doFollow(Player.java:2376)
	at server.model.players.Client.process(Client.java:895)
	at server.core.PlayerHandler.process(PlayerHandler.java:135)
	at server.Server$1.execute(Server.java:156)
	at server.core.GameEngine$1.run(GameEngine.java:47)
	at server.core.GameEngine$5.run(GameEngine.java:112)
	at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
	at java.util.concurrent.FutureTask.run(Unknown Source)
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(Unknown Source)
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(Unknown Source)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)