Search box not working as expected in Ember tutorial app

I just worked my way through the Ember tutorial app. The only thing that does not work as expected is the search box. It happens from time to time that not all data is displayed if I hit backspace multiple times to clear the search box.

After pressing Backspace all data is than displayed again.

BTW: The final tutorial app from GitHub (http://ift.tt/2ppsuFa) shows the same problem.