PyQt6 ValueError in QWidget.windowFlags

[Ales Erjavec]

Hi,

The following code fails with a 'ValueError ... is not a WindowType'
in `windowFlags()` call:
```
from PyQt6.QtCore import Qt
from PyQt6.QtWidgets import QApplication, QWidget

app = QApplication([])

w = QWidget()
w.windowFlags()  # << error
```

Windows 10
Python 3.8.8
PyQt6 6.1.0.dev2104191430

Best wishes
Aleš Erjavec