There is currently an issue in h where the search API call may sometimes return
pages that are incomplete, even if there are more pages of results to fetch
afterwards [1]. A non-full page caused the client to stop fetching more pages as
it incorrectly assumed it had reached the end. Ultimately this needs to be
resolved in the API [2] by adding an explicit next-page link. Until that is done,
change the client to continue paging through results as long as the current page
has at least one entry (needed to construct the cursor) and we expect more
results based on the `total` value in the response.

Fixes https://github.com/hypothesis/client/issues/5219

[1] https://github.com/hypothesis/h/issues/7840
[2] https://github.com/hypothesis/h/issues/7841