Fixed bugs when Artist or Album not supplied for song

libremsonic/app.py

@@ -761,9 +761,14 @@ class LibremsonicApp(Gtk.Application):
                     self.window.present()
 
                 try:
+                    notification_lines = []
+                    if song.album:
+                        notification_lines.append(f'<i>{song.album}</i>')
+                    if song.artist:
+                        notification_lines.append(song.artist)
                     song_notification = Notify.Notification.new(
                         song.title,
-                        f'<i>{song.album}</i>\n{song.artist}',
+                        '\n'.join(notification_lines),
                     )
                     song_notification.add_action(
                         'clicked',

libremsonic/dbus_manager.py

@@ -265,9 +265,9 @@ class DBusManager:
             'mpris:trackid': '/song/' + song.id,
             'mpris:length': duration,
             'mpris:artUrl': CacheManager.get_cover_art_url(song.id, 1000),
-            'xesam:album': song.album,
-            'xesam:albumArtist': [song.artist],
-            'xesam:artist': [song.artist],
+            'xesam:album': song.album or '',
+            'xesam:albumArtist': [song.artist or ''],
+            'xesam:artist': [song.artist or ''],
             'xesam:title': song.title,
         }