Comment 5 for bug 797795

No, I don't mean that GUI disappears. Just the Top Window Menu. As you can see in screenshots. Notice the mouse on top left corner of the screen. It displays it nicely when I start qbittorrent with no other windows running. For example: qbittorrent is running in the background. I have a white-list for all apps that run in systray. I click on qbittorrent icon in systray and point with mouse over window menu. You know, upper panel wit exit, maximize and minimize buttons. At this point window menu shows.
But when I have qbittorrent running in background and open other windows or app (like firefox or simply nautilus), and then click on qbittorrent icon in systray, upper panel window menu (with selections like file, tools...) is gone. When I point with mouse over it, qbittorrent version number disappears and panel ( where it should show window menu with: file, tools...) is blank.

It seems this is the problem for all Qt apps. Do a white-list for systray icons and try to run some Qt app couple of times in combination with firefox for example and you will reproduce it successfully.