Hopper beneath furnace doesn't remove empty buckets

If a hopper is feeding smeltable items from the top, and a hopper is feeding Lava Buckets from the side, when the lava is emptied from the bucket, the empty bucket stays in the fuel slot and blocks any further smelting. I think it would be better to make an exception for the hopper beneath a furnace so it will pull an item from the fuel slot if that item is an empty bucket. Also, bugs aside, I think the hopper is an excellent idea. Keep up the good work.