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.
Identity of a list item is determined by `itemDataPath` when an object is passed as an argument to a method of list view. I thought keeping the same behavior in similar views would be consistent semantically. Equality operator is not always enough to determine same object.