[YT] Some links chapters parameter is Null

[someziggyman]

Checklist

• [x] I'm reporting a broken site support issue
• [x] I've verified that I'm running youtube-dlc version 2020.10.31
• [x] I've checked that all provided URLs are alive and playable in a browser
• [x] I've checked that all URLs and arguments with special characters are properly quoted or escaped
• [x] I've searched the bugtracker for similar bug reports including closed ones
• [x] I've read bugs section in FAQ

Verbose log

./youtube-dlc -J https://www.youtube.com/watch?v=PSy62MExgQE&t=155s
 {"upload_date": "20150417", "subscriber_count": 222000, "extractor": "youtube", "chapters": null, "height": 720, "playlist_index": null, "view_count": 155701, "playlist": null, "title": "Classic Ballet Class Center Workout | Kathryn Morgan" ..... 

Description

Most videos chapter parameters are extracted correctly, but some are NULL. No idea why. Maybe, there are several ways timecodes/chapters can be tagged in code or something. Please see 2 sample links below:

Example1 with NULL chapters: https://www.youtube.com/watch?v=PSy62MExgQE

Example 2 with non-null chapters: https://www.youtube.com/watch?v=Q9yn1DpZkHQ

[pukkandan]

Youtube also doesnot recognize that video's chapters. I guess the formatting is wrong?