After updating the Qt version from Qt 5.13.0 to Qt 5.14 I started to get this printout
file:///home/plover/test_workspace/testQt5.14/main.qml:12:9: Unable to assign QJSValue to QVector<QPointF>
And sure enough, the TestQuickItem is no longer displayed on screen.
When compiling with Qt 5.13.0 this issue does not occur, and the TestQuickItem is displayed.
Attached is a minimal example test-application I created, that shows this clearly. Change the Qt5_DIR from 5.13 to 5.14 and the issue occurs.