Address Book example crashes on exit

To repro:

• Launch the Address Book Example (examples/widgets/itemviews/addressbook)
• Press the [Add] button
• Type in "Batman" -> "Gotham City" (it should display Batman under the "ABC" tab)
• File -> Exit

=> "addressbook quit unexpectedly"

Notice it also happens even with "Superman". But then you need to change to the "STU" tab before exiting. So it seems to not crash if a tab that has an empty itemview visible when you exit.