5.9.4 snapshot breaks QQuickWidget mouse inputs (MouseArea)

When migrating our QQuickWidget based application from to 5.9.4, our QML MouseArea instances stopped working!

How to reproduce:

1. Open "Qt Quick Widgets Example"
2. Add the following lines to rotatingsquare.qml
   MouseArea {
   id: mouse
   enabled: true
   anchors.fill: parent
   onClicked:  console.log('clicked')
   onPressed:  console.log('pressed')
   onReleased: console.log('released')
   }
3. Run the application and click on the red rectangle.

Problem:

No mouse events are detected.
The events works as expected using Qt 5.9.3.