Furnace: Start the timer on on_metadata_inventory_take (#2639)

This fixes a cosmetic issue where if a player removes
items from the furnace it will not revert to showing that its
"Empty". The furnace would only show its empty when the the
items were used up by the smelting process.

mods/default/furnace.lua

@@ -318,6 +318,10 @@ minetest.register_node("default:furnace", {
 		-- start timer function, it will sort out whether furnace can burn or not.
 		minetest.get_node_timer(pos):start(1.0)
 	end,
+	on_metadata_inventory_take = function(pos)
+		-- check whether the furnace is empty or not.
+		minetest.get_node_timer(pos):start(1.0)
+	end,
 	on_blast = function(pos)
 		local drops = {}
 		default.get_inventory_drops(pos, "src", drops)