Fixed another crash that was similar to the last one.

The crash occurred when the temporary playlist got deleted and then loaded again. It occurred because library.temporary_playlist didn't get set to None on deletion.

wobuzz/player/playlist.py

@@ -312,6 +312,9 @@ class Playlist:
         for track in self.tracks:  # remove items that corresponded to the track and this playlist
             track.delete_items(self)
 
+        if self == self.app.library.temporary_playlist:
+            self.app.library.temporary_playlist = None
+
         self.app.utils.unique_names.remove(self.title)
         self.app.library.playlists.remove(self)