minor php glitch

Occasionally, when you try to go to the latest post in a thread, and if that post is on the bottom of a page, php will direct you to a new page.

For instance this link is wrong: www.abovetopsecret.com...

Post 1398883 is on page 6, not page 7, so the link goes to a blank page.

Once another post is added, the error will disappear.