Filter for QML types can't be cleared

1. Open a QML file in Design mode.
2. In the Library view, see the "QML Types" tab
   You'll see three qroups:

• Qt Quick - Basics
• Qt Quick - Positioner
• Qt Quick - Views

1. I the "Filter" edit, type an "h" and remove it.
   You'll only see "Qt Quick - Views"
2. I the "Filter" edit, type a "b" and remove it.
   You'll only see "Qt Quick - Basics"
3. I the "Filter" edit, type a "y" and remove it.
   The list will be empty.

Clearing the filter should make all items visible again.

Found by Henri