CTR Theme not properly registered

Warning: Cannot modify header information - headers already sent by (output started at /home/bravebea/public_html/insurance-for-landlords.net/wp-content/themes/ctr-theme/functions.php:431) in /home/bravebea/public_html/insurance-for-landlords.net/wp-includes/class-IXR.php on line 372
XML-RPC server accepts POST requests only.