Error message on blog page if no category set

If I do not set a specific category to display on the blog page, I get this error message on top op the page:

Warning: implode() [function.implode]: Invalid arguments passed in /home/deb34820/domains/bsmeets.com/public_html/newsite/wp-content/themes/HighendWP/page-blog.php on line 35

see attached image

But I want to show all blog posts, I don’t think I would need to manually select all categories in order for this to work?

Thanks for your help!