public function update( $value ) {
global $custom_image_header;
+ // If _custom_header_background_just_in_time() fails to initialize $custom_image_header when not is_admin().
+ if ( empty( $custom_image_header ) ) {
+ require_once( ABSPATH . 'wp-admin/custom-header.php' );
+ $args = get_theme_support( 'custom-header' );
+ $admin_head_callback = isset( $args[0]['admin-head-callback'] ) ? $args[0]['admin-head-callback'] : null;
+ $admin_preview_callback = isset( $args[0]['admin-preview-callback'] ) ? $args[0]['admin-preview-callback'] : null;
+ $custom_image_header = new Custom_Image_Header( $admin_head_callback, $admin_preview_callback );
+ }
+
// If the value doesn't exist (removed or random),
// use the header_image value.
if ( ! $value )