Ubuntu: QSystemTray choices the primal button for the further interaction

test case: 
1 . take system tray example from here qtbase/widgets/desktop/systray 

2. in 

void Window::createTrayIcon()

 replase this code 

trayIconMenu->addAction(minimizeAction); 
trayIconMenu->addAction(maximizeAction); 
trayIconMenu->addAction(restoreAction);

with this

QMenu* m = trayIconMenu->addMenu("menu"); 
m->addAction(minimizeAction); 
m->addAction(maximizeAction); 
m->addAction(restoreAction);

3. run app

4. a. right click on system tray icon ( hart ) and hover submenu "menu" to open it

    b. left click on element in submenu

    resault: action doesn't trigger

5. a. left click on system tray icon ( hart ) and hover submenu "menu" to open it

    b. right click on element in submenu

    resault: action doesn't trigger

6. a. right click on system tray icon ( hart ) and hover submenu "menu" to open it

    b. right click on element in submenu

    resault: action triggers

7. a. left click on system tray icon ( hart ) and hover submenu "menu" to open it

    b. left click on element in submenu

    resault: action triggers