[Reg 5.9.6->5.11.1]QDockWidget resizes if main window size is changed

There is a defect when user resizes the main window, dockwidget size is reset to original. 

Steps to reproduce it:

1. Open the app
2. Resize the width of the 'Test' dock widget (make it wider)
3. Resize the main window in any way (even one pixel wider or taller) -> Dock widget width reset.

This defect is 5.10.1 onward. Its working fine in 5.9.5 and 5.6.1