System tray icon doesn't work under Plasma 5
The system tray icon does not work under Plasma Desktop 5.x, because Plasma 5 no longer supports the old XEmbed-based system tray icons.
Due to this, closing the window by means of the window manager (like pressing Alt+F4 or clicking the usual 'X' button in the window frame) will hide the program but will not close it properly. You also can't get it to show again.
The icon issue is resolved by building Dianara with Qt 5.x, but this is not fully supported at the moment (it works if running with qoauth-qt5, but most GNU distributions don't ship that yet).
For 1.3.0, Dianara should be made aware of the unavailability of the systray icon, so it will close properly when closing the window in any way.