Bug 926105 - When there are no apps to show in the app switcher, show a text saying "No recent apps"

As reported by @elad661 at Bugzilla:
>Steps to reproduce:
1) Long press the home button

>Actual results:
Screen darkens. Nothing shows on the darkened screen.

>Expected results:
I'd expect some text informing me that there are no apps to show, instead of an empty semi transparent overlay.