L2J Server

Hello and sorry for posting here but i don't have enough post to post it on Bugs Section
please if any mod can move it to right section thank you.

All is loading ok on console but in the end after some seconds it show me this error

• Exception in thread "AISTPool-3" java.lang.NullPointerException
  at com.l2jserver.gameserver.model.actor.L2Npc.doDie(L2Npc.java:1526)
  at com.l2jserver.gameserver.model.actor.L2Attackable.doDie(L2Attackable.
  java:525)
  at com.l2jserver.gameserver.model.actor.instance.L2MonsterInstance.doDie
  (L2MonsterInstance.java:161)
  at ai.group_template.DenOfEvil$KashaDestruction.destroyZone(DenOfEvil.ja
  va:222)
  at ai.group_template.DenOfEvil$KashaDestruction.run(DenOfEvil.java:203)
  at com.l2jserver.gameserver.ThreadPoolManager$RunnableWrapper.run(Thread
  PoolManager.java:86)
  at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
  at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)
  at java.util.concurrent.FutureTask.run(Unknown Source)
  at java.util.concurrent.ScheduledThreadPoolExecutor$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)

I don't have any error on eclipse all it looks fine can anyone help me with this please
because i don't know where to search for a solution thank you in advance guys
and sorry again for wrong section.

check L2Npc.java line 1526. whats there?

is this

//If killer instanceof L2PetInstance or instanceof L2SummonInstance, this is going to get the player that controls the killer.
L2PcInstance player = null;
player = killer.getActingPlayer(); <--------- this is the line 1526

Try this