Rows read in the Unread view (or unstarred in Starred, untagged in a
tag view) stay on screen, but they have left the server's result.
`loadMoreEmails` still counted them in `position`, so the next page
started that many messages too late, and the `emails.length >= total`
guard could stop paging while server rows were still unloaded.
Page from the number of loaded rows the query still returns, like the
webmail, and take the total from the load-more query so a list that
shrank under the user doesn't keep asking for a page that isn't there.
Linus Rath
35e0792558