Custom Page Pagination

Hoping someone can help me with a problem. I am using a custom page to display all posts with pagination, I noticed last night in webmaster tools that I am getting some soft 404’s from the custom page. After looking at the soft 404 I have realised that instead of stopping at the last page the rel next/prev is pointing to the next page, even though pagination isn’t.

When I visit any page after the last paginated page I am getting the “no posts found” instead of a 404.

This is the code I am using http://pastebin.com/q5aUQ3HP

Would appreciate any help.

Thanks