autocomplete: clear active item after selection

After an item is chosen, we should clear the selected item in the list view. The implementation is a little weird. I noticed that code was pretty old that I was editing :). This fixes a bug where the same item will be selected multiple times when it shouldn't be.
Sorry, I would make the change myself, but I wasn't able to grok your suggestion. I don't understand how I should check the identity of the object by the item data path, which is just a string.