"Shrug off" fix

(Seriously, no one noticed it before? O_O)
This fixes shrugoffs to work for a player and not just write a message in chat.
So I was testing my addon, and witnessed shrrugs off happen but not happen. I added lots of debug output, but the return value of Actor.on_set_temporary_effect seemed to just disappear. Then I remembered something might've overloaded it.... and there I am!
(It worked when shrugs off still worked by setting dur to 0, I imagine. It also worked for NPCs.)