Update functions.js subtitles by button turned out dead end

[raszpl]

#2400 button was still fragile and breaking :(. The only bulletproof ways of learning if subtitles are available are

player.getOption('captions', 'tracklist', {includeAsr: true})
player.getSubtitlesUserSettings() 

also player.isSubtitlesOn() does work even if video has no subtitles, and player.toggleSubtitlesOn() is ignored in same case making both safe to call without checking.

[ImprovedTube]

so it sounds like the method might not even be of use as a backup?

[raszpl]

player.getSubtitlesUserSettings() is in my tests 100% reliable. player with no subtitles available doesnt posses any 'Subtitles User Settings' and returns null