Scraper is failing on empty playlist

[benoit74]

While the scraper should simply ignore empty playlist (and not even render them in the final ZIM UI), currently the scraper fails when it encounters an empty playlist:

[youtube2zim::2024-09-21 21:01:47,936] ERROR:Interrupting process due to error: list index out of range
[youtube2zim::2024-09-21 21:01:47,936] ERROR:list index out of range
Traceback (most recent call last):
  File "/usr/local/lib/python3.12/site-packages/youtube2zim/scraper.py", line 421, in run
    self.make_json_files(succeeded)
  File "/usr/local/lib/python3.12/site-packages/youtube2zim/scraper.py", line 1177, in make_json_files
    playlist_list.append(generate_playlist_preview_object(playlist))
                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.12/site-packages/youtube2zim/scraper.py", line 1135, in generate_playlist_preview_object
    videos[0]["contentDetails"]["videoId"]
    ~~~~~~^^^
IndexError: list index out of range