Ignore DBuxException when sending a notification

Because sending notifications is not the main feature, backintime should
continue to work when that fails.

Idea from #1156 (comment)

qt/plugins/notifyplugin.py

@@ -54,7 +54,10 @@ def isGui(self):
         return True
 
     def message(self, profile_id, profile_name, level, message, timeout):
-        notify_interface = dbus.Interface(object=dbus.SessionBus().get_object("org.freedesktop.Notifications", "/org/freedesktop/Notifications"), dbus_interface="org.freedesktop.Notifications")
+        try:
+            notify_interface = dbus.Interface(object=dbus.SessionBus().get_object("org.freedesktop.Notifications", "/org/freedesktop/Notifications"), dbus_interface="org.freedesktop.Notifications")
+        except dbus.exceptions.DBusException:
+            return
         if 1 == level:
             if timeout > 0:
                 timeout = 1000 * timeout
@@ -63,5 +66,8 @@ def message(self, profile_id, profile_name, level, message, timeout):
             title = "Back In Time (%s) : %s" % (self.user, profile_name)
             message = message.replace("\n", ' ')
             message = message.replace("\r", '')
-            notify_interface.Notify("Back In Time", 0, "", title, message, [], {}, timeout)
+            try:
+                notify_interface.Notify("Back In Time", 0, "", title, message, [], {}, timeout)
+            except dbus.exceptions.DBusException:
+                pass
         return