This bug is triggered by empathy either 2.26 and 2.27
the task list entry of empathy disappears when the empathy main window is closed (this is normal), but it does not appear when it is restored by clicking on its tray icon.
This happens only with compiz as the window manager.
this patch makes empathy work correctly, but the developers think that it should be fixed here instead of in empathy, because this is only a workaround, and the real bug lands here
Mass closure: This bug has been untouched for more than six years, and is not
obviously still valid. Please reopen this bug or file a new report if you continue to experience issues with current releases.