Warning: Trying to access array offset…

Just began setting up this site on a new web host. I’d set it up on a “free” host just so we could show the client how the site would look. He loved it, and decided to let us proceed with Longevity. Everything worked fine on the free hosting site. But now that I have it installed on the new host, every page is throwing an error message at the top: “Warning: Trying to access array offset on value of type bool in /homepages/11/d4296865125/htdocs/wordpress/wp-content/themes/longevity/template-parts/headers.php on line 28”

The page I need help with: [log in to see the link]