Still skipping any renditions that have a null URL, which means that
closedCaptions in particular is always empty. This restriction will
be removed in a subsequent change, which will also remove muxedAudioFormat
and muxedAudioCaptions from HlsMasterPlaylist and instead derive them
from the Variant and Rendition information in HlsMediaPeriod.
Issue: #5596
Issue: #2600
PiperOrigin-RevId: 240623500
