Fatal Error

Can someone help solve this problem please?

Every time I try to upgrade from Customizr 3.4.23 to 3.5.4 I get the error below and then have to restore. Everything else updates fine and the site works normally even after a WP core update (currently on 4.7.2)

Fatal error: Uncaught Error: Class ‘TC_post_list’ not found in /var/sites/n/natureheals.co.uk/public_html/wp-content/themes/customizr-child/functions.php:31 Stack trace: #0 /var/sites/n/natureheals.co.uk/public_html/wp-includes/class-wp-hook.php(298): exclude_images_from_search_results(”) #1 /var/sites/n/natureheals.co.uk/public_html/wp-includes/class-wp-hook.php(323): WP_Hook->apply_filters(NULL, Array) #2 /var/sites/n/natureheals.co.uk/public_html/wp-includes/plugin.php(453): WP_Hook->do_action(Array) #3 /var/sites/n/natureheals.co.uk/public_html/wp-settings.php(449): do_action(‘init’) #4 /var/sites/n/natureheals.co.uk/public_html/wp-config.php(117): require_once(‘/var/sites/n/na…’) #5 /var/sites/n/natureheals.co.uk/public_html/wp-load.php(37): require_once(‘/var/sites/n/na…’) #6 /var/sites/n/natureheals.co.uk/public_html/wp-blog-header.php(13): require_once(‘/var/sites/n/na…’) #7 /var/sites/n/natureheals.co.uk/public_html/index.php(17): require(‘/var/sites/n/na…’) #8 {main} thrown in /var/sites/n/natureheals.co.uk/public_html/wp-content/themes/customizr-child/functions.php on line 31