a few qdel_null's

code/game/machinery/vending.dm

@@ -546,12 +546,10 @@
 				to_chat(user, "<span class='notice'>You successfully pull the coin out before the [src] could swallow it.</span>")
 			else
 				to_chat(user, "<span class='notice'>You weren't able to pull the coin out fast enough, the machine ate it, string and all.</span>")
-				coin = null
-				qdel(coin)
+				QDEL_NULL(coin)
 				categories &= ~CAT_COIN
 		else
-			coin = null
-			qdel(coin)
+			QDEL_NULL(coin)
 			categories &= ~CAT_COIN
 
 	R.amount--

code/game/objects/items/weapons/RCD.dm

@@ -279,8 +279,7 @@ RCD
 					return 0
 				activate()
 				var/turf/T1 = get_turf(A)
-				qdel(A)
-				A = null
+				QDEL_NULL(A)
 				for(var/obj/structure/window/W in T1.contents)
 					W.disassembled = 1
 					W.density = 0

code/game/objects/items/weapons/grenades/smokebomb.dm

@@ -14,8 +14,7 @@
 		src.smoke.attach(src)
 
 	Destroy()
-		qdel(smoke)
-		smoke = null
+		QDEL_NULL(smoke)
 		return ..()
 
 	prime()