! Fix assorted Recent Posts bugs

This fixes #1378 and one other issue.

Specifics:
* Pagination was incorrect in many situations
* No message was shown when there weren't any posts to display
* Posts from ignored boards and the recycling bin (if you could view it) were being included when viewing recent posts in a specific category or categories

Signed-off-by: Michael Eshom <oldiesmann@oldiesmann.us>