[subtitles] Fix CC condition for valid captions

[enen92]

Description

"Borrowed" from VLC (videolan/vlc@67dd763) this attempts to fix the condition used to let the demuxing of closed captions proceed.

Motivation and context

A user reported the bug and provided a sample file in https://forum.kodi.tv/showthread.php?tid=368221
Kodi is unable to show those captions while vlc or mpv play them without any issues.

How has this been tested?

Runtime tested, played some samples I knew Kodi was able to handle before + the failing one.

What is the effect on users?

Some CC subs that were previously not playing should now be playable.

Screenshots (if appropriate):

Master:

PR:

Types of change

• Bug fix (non-breaking change which fixes an issue)
• Clean up (non-breaking change which removes non-working, unmaintained functionality)
• Improvement (non-breaking change which improves existing functionality)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that will cause existing functionality to change)
• Cosmetic change (non-breaking change that doesn't touch code)
• None of the above (please explain below)

[CastagnaIT]

Thanks! I have been circling this issue for a long time

now CC subtitles works also with InputStreamAdaptive
tested with: https://livesim.dashif.org/dash/vod/testpic_2s/cea608.mpd
great!

PS. please PM me the CC sample video i am not able download it