I have read this error in console but I do not understand because

Exception in thread "GeneralSTPool-5" java.lang.NullPointerException
at com.l2jserver.gameserver.model.entity.ClanHall.banishForeigners(ClanH
all.java:411)
at com.l2jserver.gameserver.model.entity.clanhall.ClanHallSiegeEngine.st
artSiege(ClanHallSiegeEngine.java:346)
at com.l2jserver.gameserver.model.entity.clanhall.ClanHallSiegeEngine$Si
egeStarts.run(ClanHallSiegeEngine.java:512)
at com.l2jserver.gameserver.ThreadPoolManager$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)
GlobalVariablesManager: Database updated.
Tnx