Fix SpotifyIterator failing on None type tracks.

Author: EvieePy

wavelink/ext/spotify/__init__.py

@@ -144,6 +144,9 @@ async def __anext__(self):
         except asyncio.QueueEmpty:
             raise StopAsyncIteration
 
+        if track is None:
+            return await self.__anext__()
+
         if self._partial:
             track = PartialTrack(query=f'{track["name"]} - {track["artists"][0]["name"]}')
         else: