Fatal error: Uncaught TypeError: call_user_func_array(): Argument #1 ($callback) must be a valid callback, function "_custom_background_cb" not found or invalid function name in /var/www/vhosts/mannatgears.ca/httpdocs/wp-includes/class-wp-hook.php:324 Stack trace: #0 /var/www/vhosts/mannatgears.ca/httpdocs/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters() #1 /var/www/vhosts/mannatgears.ca/httpdocs/wp-includes/plugin.php(517): WP_Hook->do_action() #2 /var/www/vhosts/mannatgears.ca/httpdocs/wp-includes/general-template.php(3192): do_action() #3 /var/www/vhosts/mannatgears.ca/httpdocs/wp-content/themes/flozen-theme/headers/header-main.php(16): wp_head() #4 /var/www/vhosts/mannatgears.ca/httpdocs/wp-content/themes/flozen-theme/cores/nasa-theme-headers.php(142): include_once('...') #5 /var/www/vhosts/mannatgears.ca/httpdocs/wp-includes/class-wp-hook.php(324): flozen_get_header_theme() #6 /var/www/vhosts/mannatgears.ca/httpdocs/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters() #7 /var/www/vhosts/mannatgears.ca/httpdocs/wp-includes/plugin.php(517): WP_Hook->do_action() #8 /var/www/vhosts/mannatgears.ca/httpdocs/wp-content/themes/flozen-theme/header.php(8): do_action() #9 /var/www/vhosts/mannatgears.ca/httpdocs/wp-includes/template.php(810): require_once('...') #10 /var/www/vhosts/mannatgears.ca/httpdocs/wp-includes/template.php(745): load_template() #11 /var/www/vhosts/mannatgears.ca/httpdocs/wp-includes/general-template.php(48): locate_template() #12 /var/www/vhosts/mannatgears.ca/httpdocs/wp-content/themes/flozen-theme/woocommerce/single-product.php(9): get_header() #13 /var/www/vhosts/mannatgears.ca/httpdocs/wp-includes/template-loader.php(106): include('...') #14 /var/www/vhosts/mannatgears.ca/httpdocs/wp-blog-header.php(19): require_once('...') #15 /var/www/vhosts/mannatgears.ca/httpdocs/index.php(17): require('...') #16 {main} thrown in /var/www/vhosts/mannatgears.ca/httpdocs/wp-includes/class-wp-hook.php on line 324