Fixes airlock icon state/animation weirdness

door_spark and door_deny icon states are usually of a closed door, so it
looks glitchy if they are used when the door is open (such as by pulsing
the ID scan wire).

code/game/machinery/doors/airlock.dm

@@ -648,8 +648,10 @@ About the new airlock wires panel:
 			else
 				flick("door_closing", src)
 		if("spark")
+			if(density)
 				flick("door_spark", src)
 		if("deny")
+			if(density)
 				flick("door_deny", src)
 	return