Stop non-damaging spell projectiles from stealing NPC aggression

Right now non-damaging projectiles have the capability to override the aggression of a NPC, unlike damaging projctiles which check if the NPC is otherwise engaged first.

This can be abused to lure players who are safe-spotting at the king black dragon by casting a curse spell to steal the NPC's aggression, then logging out so that it wanders freely again.