save/restore doesn't work when QMainWindow is maximized

1. Please build and run the attached sources.
2. Maximize the mainwindow
3. Resize dock widgets
4. Close application
5. Run the application again

Expected result: The newly run application look should be the same like it was before closed earlier

Current result: The newly run application is looking differently

Notes:

• if the central widget is removed, then it works correctly
• saving and restoring central widgets geometry doesn't help