Expected behavior

Tags that have already been used in the navigation should not show up in the auto-complete dropdown.

Actual Behavior

When adding new tags into the navigation, the auto-complete feature shows tags that have already been used. When you click on an already used tag, it just kind of disappears and nothing happens.

Steps to Reproduce the Behavior

Add new tags to a product or the nav. Try to add the same tag again, and see it show up in the auto-complete dropdown.