pages: Fix incorrect lookup of inline images

In some cases, a POST might be sent to the server and there be no draft. In
such a case, neither the draft nor the body of the page can be inspected for
images. Even worse, in some cases the previous images might be unlinked from
the article without being relinked. Therefore, the images will no longer be
linked to the page and will likely be purged from the system.
Merge pull request #1288 from greezybacon/oops/page-images

pages: Fix incorrect lookup of inline images

Reviewed-By: Peter Rotich <peter@osticket.com>