Merge pull request #4172 from out-of-phaze/fix/magshield-jam

Fix runtime when sabotaging a magnetic field generator with metal rods

maps/away/magshield/magshield.dm

@@ -103,9 +103,10 @@
 		sleep(50)
 		visible_message(SPAN_DANGER("\The [src] explodes!"))
 		var/turf/T = get_turf(src)
-		explosion(T, 2, 3, 4, 10, 1)
 		empulse(src, heavy_range*2, lighter_range*2, 1)
-		qdel(src)
+		explosion(T, 2, 3, 4, 10, 1)
+		if(!QDELETED(src))
+			qdel(src)
 	if(istype(W, /obj/item/mop))
 		to_chat(user, SPAN_NOTICE("You stick \the [W] into the rotating spokes, and it immediately breaks into tiny pieces."))
 		qdel(W)