The watch frame alone read as "nothing related" — so a related column YouTube moved, or a list
drawn by renderers this does not read, answered an empty list instead of an error. Now only the
"isn't available" promo YouTube draws for a video it no longer has is an empty page; anything else
it cannot read is a ScrapeError.
The flattening of a video renderer and the read of the continuation token are one each, in
innertube, for the search and the related scrape.