Fix posibrain not turning off if no candidate

The reset proc was checking for the presence of a brainmob, while one
was created in the constructor. It should rather check the presence of a
key

code/modules/mob/living/carbon/brain/posibrain.dm

@@ -65,7 +65,7 @@
 
 	proc/reset_search() //We give the players sixty seconds to decide, then reset the timer.
 
-		if(brainmob) return
+		if(src.brainmob.key) return
 
 		src.searching = 0
 		icon_state = "posibrain"