[QML] Gray rectangle appear on Map when Menu is displayed

1. Make a qml file that contains a Map object and a ComboBox (or other just a Menu) from Quick controls 2.
2. Click on the ComboBox to display the options
3. Hover with mouse or keys over the options from the list (while the ComboBox is expanded)
4. Observer the map

While moving the mouse two behaviours were observed:

• A gray / white rectangle appears on the map and remains visible until the Menu is remove
• On other systems the rectangle flickers (appears / disappears) each time a new MenuItem is hovered.