[Nez]

Всем привет! Подскажите пожалуйста о чем говорит ошибка.
Выскакивает когда бьешь моба на ХБ он остается с 0 хп и летит ошибка.
Хроники IO

[06.08.16 04:19:04:858] ERROR model.Creature: 
java.lang.NullPointerException
	at l2s.gameserver.model.instances.MonsterInstance.calculateRewards(MonsterInstance.java:441)
	at l2s.gameserver.model.instances.MonsterInstance.onDeath(MonsterInstance.java:307)
	at l2s.gameserver.model.Creature.doDie(Creature.java:1838)
	at l2s.gameserver.model.Creature.onReduceCurrentHp(Creature.java:3751)
	at l2s.gameserver.model.instances.NpcInstance.onReduceCurrentHp(NpcInstance.java:285)
	at l2s.gameserver.model.instances.MonsterInstance.onReduceCurrentHp(MonsterInstance.java:336)
	at l2s.gameserver.model.Creature.reduceCurrentHp(Creature.java:3700)
	at l2s.gameserver.skills.skillclasses.MDam.useSkill(MDam.java:27)
	at l2s.gameserver.model.Skill.onEndCast(Skill.java:2889)
	at l2s.gameserver.model.Creature.callSkill(Creature.java:1158)
	at l2s.gameserver.model.Playable.callSkill(Playable.java:533)
	at l2s.gameserver.model.Creature.onMagicUseTimer(Creature.java:3465)
	at l2s.gameserver.model.GameObjectTasks$MagicUseTask.runImpl(GameObjectTasks.java:348)
	at l2s.commons.threading.RunnableImpl.run(RunnableImpl.java:21)
	at java.util.concurrent.Executors$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)
	at l2s.commons.threading.PriorityThreadFactory$1.run(PriorityThreadFactory.java:35)