Hoppers can't remove empty bottles left in brewing stands when brewing lingering potions with Dragon's Breath.

To replicate, have a splash potion in the bottom of a brewing stand then put Dragon's Breath in the top. Once it is finished brewing, place/activate a hopper beneath the brewing stand and observe that the hopper will remove the potions but not the empty bottle.
I have a video quickly demonstrating the bug here:
http://youtu.be/dV5AiuHucV0

This could be intended behavior, but I doubt it because it contrasts with the hopper's ability to remove empty buckets in furnaces left by using lava buckets as fuel.

This bug is a problem because it prevents automatic brewing machines from making lingering potions. I demonstrate such a broken machine here:
https://youtu.be/dj_R3xEj1-o