makes w_class use defines (#9848)

code/modules/reagents/reagent_containers/inhaler.dm

@@ -11,7 +11,7 @@
 	unacidable = 1
 	amount_per_transfer_from_this = 5
 	volume = 5
-	w_class = 2
+	w_class = ITEMSIZE_SMALL
 	possible_transfer_amounts = null
 	flags = OPENCONTAINER
 	slot_flags = SLOT_BELT
@@ -232,4 +232,4 @@
 		. =..()
 		reagents.add_reagent(/datum/reagent/pneumalin, volume)
 		update_icon()
-		return
+		return