reset window title every time we change the state of a subwindow to show the correct title

When maximizing a subwindow it remembers the title the mainwindow had before and resets it after unmaximizing/closing.
As the title might have changed due to a project switch, we have to reset the title again as it would else show an incorrect/old title.
Merge pull request #1479 from DanWin/title

reset window title every time we change the state of a subwindow to show...