feat: add delete function

media/cache.py

@@ -73,7 +73,7 @@ class MusicCache(dict):
         return items
 
     def fetch(self, bot, id):
-        music_dicts = self.db.query_music(Condition().and_equal("id", id))
+        music_dicts = self.db.query_music_by_id(id)
         if music_dicts:
             music_dict = music_dicts[0]
             self[id] = dict_to_item(bot, music_dict)

media/playlist.py

@@ -268,9 +268,9 @@ class OneshotPlaylist(BasePlaylist):
         return self
 
     def next(self):
-        self.version += 1
-
         if len(self) > 0:
+            self.version += 1
+
             if self.current_index != -1:
                 super().__delitem__(self.current_index)
                 if len(self) == 0: