Rendering the title broken if there are two monitors and the main screen is turned off

This is a bug with windows used extended title bar.
Seems like DC was not updated.

Use qtbase\examples\widgets\dialogs\classwizard example to reproduce
the bug.

Steps to reproduce:

• attach auxiliary monitor;
• extend Desktop on both screens;
• make the auxiliary monitor as main screen;
• run sample on main screen. See attached start.png;
• turn off the auxiliary monitor in preferencies, i.e. show Desktop only
  on the initial monitor. See result on the attached screenshot
  result.png.