Merge pull request #45 from alex-gh/stacker_fix

Stacker fix

code/game/objects/items/stacks/stack.dm

@@ -17,7 +17,7 @@
 
 /obj/item/stack/New(var/loc, var/amount=null)
 	..()
-	if (amount)
+	if (amount!=null)	//Allow for stacks with the amount=0
 		src.amount=amount
 	return
 

code/modules/mining/machine_stacking.dm

@@ -102,9 +102,11 @@
 
 
 /obj/machinery/mineral/stacking_machine/process()
-	var/obj/item/stack/sheet/O
-	while (locate(/obj/item/stack/sheet, input.loc))
-		O = locate(/obj/item/stack/sheet, input.loc)
+	var/obj/item/O
+	while (locate(/obj/item, input.loc))
+		O = locate(/obj/item, input.loc)
 		if(istype(O,/obj/item/stack/sheet))
 			process_sheet(O)
+		else
+			O.loc = src.output.loc
 	return