Ticket #35321: 35321.diff

src/wp-includes/taxonomy.php

@@ -2575 +2575 @@
         }
         $defaults = array( 'alias_of' => '', 'description' => '', 'parent' => 0, 'slug' => '');
         $args = wp_parse_args( $args, $defaults );
+        $args['description'] = (string) $args['description']; // coerce null to empty stringt
 
         if ( $args['parent'] > 0 && ! term_exists( (int) $args['parent'] ) ) {
                 return new WP_Error( 'missing_parent', __( 'Parent term does not exist.' ) );