Yet another issue with empty playlists

[benoit74]

https://farm.openzim.org/pipeline/d3ec6e04-5f5a-4c0f-8c31-4467d6508e77

[youtube2zim::2024-11-01 15:03:40,445] INFO:creating JSON files
[youtube2zim::2024-11-01 15:03:40,487] ERROR:Interrupting process due to error: list index out of range
[youtube2zim::2024-11-01 15:03:40,487] ERROR:list index out of range
Traceback (most recent call last):
  File "/usr/local/lib/python3.12/site-packages/youtube2zim/scraper.py", line 403, in run
    self.make_json_files(succeeded)
  File "/usr/local/lib/python3.12/site-packages/youtube2zim/scraper.py", line 1166, in make_json_files
    playlist_obj = generate_playlist_object(playlist)
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.12/site-packages/youtube2zim/scraper.py", line 1113, in generate_playlist_object
    videos[0]["contentDetails"]["videoId"]
    ~~~~~~^^^
IndexError: list index out of range

Looks like we did not handled the case where the playlist is expected to have a video, but for some reason it finishes empty.