[Reg 5.8 - 5.9][Windows] Assert in web_event_factory when application has a style sheet with sub-control hover defined

When the application has a style sheet with QWidget::item:hover and a QWebEngineView, following assert happens in web_event_factory.cpp in webEventTypeForEvent() when you hover over QWebEngineView:
ASSERT: "false" in file c:\users\qt\work\qt\qtwebengine\src\core\web_event_factory.cpp, line 1177

It seems that HoverEnter event causes the assert. Interestingly those events don't cause any trouble in Qt 5.8 or in macOS where this problem is not reproducible. Thus it seems that those events never go through webEventTypeForEvent() function on macOS or in Qt 5.8 while they do on Windows in Qt 5.9.

As this is an assert, it happens only in debug mode and there are no known consequences in release mode.

The attached example can be used to reproduce. Just run it in debug and hover over the app.