Remove default feature image from the page post type

/**
Remove default feature image from the page post type. Please make sure you have the Defautl Feature Image Plugin activated & enable
**/

function dfi_posttype_book ( $dfi_id, $post_id ) {
  $post = get_post($post_id);
  if ( 'wpuf-post-forms' === $post->post_type ) {
    return null; // no image
  }
  return $dfi_id; // the original featured image id
}
add_filter( 'dfi_thumbnail_id', 'dfi_posttype_book', 10, 2 );