Below is the usage and the error. It doesn't kill the script, but it happens a lot.  
  
Btw, I've replicated this by controlling the validity of the item. It doesn't happen 100%, but it does happen. 
  
  
 
[ERROR][Bot #1][07/03 12:23:09 AM]: Error in script executor!
java.lang.NullPointerException
	at org.osbot.rs07.api.util.NodeDequeIterator.set(NodeDequeIterator.java:20)
	at org.osbot.rs07.api.Map.contains(Map.java:125)
	at org.osbot.rs07.api.model.GroundItem.exists(GroundItem.java:176)
	at com.polycoding.wizardkiller.tasks.combat.Attacking.checkForLoot(Attacking.java:99)
	at com.polycoding.wizardkiller.tasks.combat.Attacking.execute(Attacking.java:46)
	at WizardKiller.onLoop(WizardKiller.java:63)
	at org.osbot.rs07.event.ScriptExecutor$InternalExecutor.run(ScriptExecutor.java:99)
	at java.lang.Thread.run(Unknown Source)