PHP Fatal Error

Ran into a problem migrating a website from an old to a new web server.  This happened months ago with Clean Education Pro v3.4.  Today, I tried installing Clean Education Pro v3.6 but got the same error.  The following is the error I get when viewing the website on a web browser: [Wed Jul 01 15:09:40.403373 2026] [php:error] PHP Fatal error: Uncaught TypeError: array_unique(): Argument #1 ($array) must be of type array, null given in mywebsitedir/wp-includes/post-template.php:871\nStack trace:\n#0 mywebsitedir/wp-includes/post-template.php(871): array_unique()\n#1 mywebsitedir/wp-includes/post-template.php(625): get_body_class()\n#2 mywebsitedir/wp-content/themes/clean-education-pro/header.php(31): body_class()\n#3 mywebsitedir/wp-includes/template.php(814): require_once('...')\n#4 mywebsitedir/wp-includes/template.php(749): load_template()\n#5 mywebsitedir/wp-includes/general-template.php(48): locate_template()\n#6 mywebsitedir/wp-content/themes/clean-education-pro/page.php(15): get_header()\n#7 mywebsitedir/wp-includes/template-loader.php(132): include('...')\n#8 mywebsitedir/wp-blog-header.php(19): require_once('...')\n#9 mywebsitedir/index.php(17): require('...')\n#10 {main}\n thrown in mywebsitedir/wp-includes/post-template.php on line 871 Thanks!  Your help is greatly appreciated.