'Last' link in HTML head always renders 1 page more than there is

Problem/Motivation

Related to pagers, the rocketship_seo module prints a link to the last page that is 1 page too far. Causing someone, like the Google bot, to follow that and to hit a page with no actual results.

Steps to reproduce

Surf to a webpage with a pager and inspect the source code.
Notice the href value at <link rel="last" href=" ends with a page number that is 1 higher than the actual last page.

Proposed resolution

Follow similar logic to what Pager->setCurrentPage() has:
$this->currentPage = max(0, min($currentPage, $this->getTotalPages() - 1));

User interface changes

None.

API changes

None.

Data model changes

None.