QScreenCapture captures window instead of screen

Reproduced on an iPad Air M2 12".

When using QScreenCapture to capture the screen, the returned frames are of the main app window, not of the actual screen. Here are the steps to reproduce:

1. Open up any QScreenCapture example.
2. Activate the the QScreenCapture 
3. Put the iPad app into Split View, and have it share the screen with any other app
4. The received frames will not include the other app, nor any system decorations (i.e status bar)

Additionally, the QScreenCapture does not respect having null for the QScreen. So you can start capturing even without setting QScreen.