also return buckets with generators

... and in the `smelt_item` function, even though it seems unused

technic/machines/register/common.lua

@@ -71,15 +71,15 @@ function technic.smelt_item(meta, result, speed)
 	if meta:get_int("cook_time") < result.time / speed then
 		return
 	end
-	local result = minetest.get_craft_result({method = "cooking", width = 1, items = inv:get_list("src")})
+	local result
+	local afterfuel
+	result, afterfuel = minetest.get_craft_result({method = "cooking", width = 1, items = inv:get_list("src")})
 
 	if result and result.item then
 		meta:set_int("cook_time", 0)
 		-- check if there's room for output in "dst" list
 		if inv:room_for_item("dst", result.item) then
-			srcstack = inv:get_stack("src", 1)
-			srcstack:take_item()
-			inv:set_stack("src", 1, srcstack)
+			inv:set_stack("src", 1, afterfuel.items[1])
 			inv:add_item("dst", result.item)
 		end
 	end

technic/machines/register/generator.lua

@@ -51,7 +51,9 @@ function technic.register_generator(data)
 			local inv = meta:get_inventory()
 			if not inv:is_empty("src") then 
 				local fuellist = inv:get_list("src")
-				local fuel = minetest.get_craft_result(
+				local fuel
+				local afterfuel
+				fuel, afterfuel = minetest.get_craft_result(
 						{method = "fuel", width = 1,
 						items = fuellist})
 				if not fuel or fuel.time == 0 then
@@ -61,9 +63,7 @@ function technic.register_generator(data)
 				end
 				meta:set_int("burn_time", fuel.time)
 				meta:set_int("burn_totaltime", fuel.time)
-				local stack = inv:get_stack("src", 1)
-				stack:take_item()
-				inv:set_stack("src", 1, stack)
+				inv:set_stack("src", 1, afterfuel.items[1])
 				technic.swap_node(pos, "technic:"..ltier.."_generator_active")
 				meta:set_int(tier.."_EU_supply", data.supply)
 			else