[REG Qt 5.11.2 -> Qt 5.12.0-beta4] Popup menus in Properties view can be shown only once

1. Open a qml file in Design mode.
2. In the Properties view, click on one of the small "nut" icons.
   A popup menu will appear:
   
3. Click somewhere else in the Properties view.
   The menu will disappear.
4. Click on the same "nut" icon again.
   The menu will not come back.

Clicking on one of the other "nut" icons will still show a menu but also only once.

I can only reproduce this with Qt Creator built on Qt 5.12.0. A Qt Creator built on Qt 5.11.2 works correctly.

The gallery example of Qt Quick Controls 1 has the same issue: