Issue when backing up playlists with exactly 50 songs

The script just goes into an infinite loop, I locally fixed this by adding a check to `get_playlist_tracks()` to make sure we aren't iterating on a redundant offset, however my code quality is trash so just making an issue:

```py
iteration = 0
while len(results["items"]) > 0 and not (results["offset"] == 0 and iteration > 0):
    iteration += 1
```

Thanks,
Elliott