Infinite loop in group picker

There's an infinite loop in the group picker if an empty query string is provided.

To reproduce, go to the people part of a project's config. Click the "add group" button to bring up the "Begin typing to find groups." text field. Type part of a group name in the group name field, and before the pop-up of options to appears, delete all the text from the text box. CPU usage should immediately spike as the infinite loop is entered.