Custom permalink gives an error after post update

[jussipalanen]

If I want to edit an existing post and save it in the WordPress dashboard. After trying to update, it gives the following error.
I use the filter hook for the post edit link.

PHP class file.

\add_filter( 'post_type_link',
    \Closure::fromCallable( [ $this, 'format_permalink' ] ),
    10,
    2
);

  /**
   * Override the permalink.
   *
   * @param string  $permalink the permalink.
   * @param WP_Post $post the post object.
   * @return string
   */
  protected function format_permalink( $permalink, $post ) {

      // This checks if the current post is a child post of the 'degree' post type.
      if ( $post->post_type === self::SLUG && ! empty( $post->post_parent ) && $post->post_parent > 0 ) {
          $parent_permalink = \get_permalink( $post->post_parent );
          if ( $parent_permalink ) {
              // For child posts, return the parent's permalink.
              return $parent_permalink;
          }
      }
      // For parent posts or other post types, return the original permalink.
      return $permalink;
  }

Lisäys epäonnistui. Uncaught Error: Attempt to assign property "permalink" on null in /app/vendor/devgeniem/dustpress/classes/query.php on line 267