QSplitter cursor doesn't show after main window changed to fullscreen on Mac

1. The main window has splitters. Hovering over the splitter handle changes the cursor to a splitter cursor, as expected.

2. Click green button at top of main window to make full screen.

3. Hovering over the QSplitter now doesn't change the cursor, even if you change back from full screen.

Works fine on Windows.

I looked at https://bugreports.qt.io/browse/QTBUG-33479 but setting qApp->setAttribute(Qt::AA_DontCreateNativeWidgetSiblings) makes no difference.