st = false;
			continue;
		}

		// Always update the revision version.
		$update = array(
			'post_name' => preg_replace( '/^(\d+-(?:autosave|revision))[\d-]*$/', '$1-v1', $this_revision->post_name ),
		);

		/*
		 * If this revision is the oldest revision of the post, i.e. no $prev_revision,
		 * the correct post_author is probably $post->post_author, but that's only a good guess.
		 * Update the revision version only and Leave the author as-is.
		 */
		if ( $prev_revision ) {
			$prev_revision_version = _wp_get_post_revision_version( $prev_revision );

			// If the previous revision is already up to date, it no longer has the information we need :(
			if ( $prev_revision_version < 1 ) {
				$update['post_author'] = $prev_revision->post_author;
			}
		}

		// Upgrade this revision.
		$result = $wpdb->update( $wpdb->posts, $update, array( 'ID' => $this_revision->ID ) );

		if ( $result ) {
			wp_cache_delete( $this_revision->ID, 'posts' );
		}
	} while ( $prev_revision );

	delete_option( $lock );

	// Add a copy of the post as latest revision.
	if ( $add_last ) {
		wp_save_post_revision( $post->ID );
	}

	return true;
}

/**
 * Filters preview post meta retrieval to get values from the autosave.
 *
 * Filters revisioned meta keys only.
 *
 * @since 6.4.0
 *
 * @param mixed  $value     Meta value to filter.
 * @param int    $object_id Object ID.
 * @param string $meta_key  Meta key to filter a value for.
 * @param bool   $single    Whether to return a single value.
 * @return mixed Original meta value if the meta key isn't revisioned, the object doesn't exist,
 *               the post type is a revision or the post ID doesn't match the object ID.
 *               Otherwise, the revisioned meta value is returned for the preview.
 */
function _wp_preview_meta_filter( $value, $object_id, $meta_key, $single ) {
	$post = get_post();

	if ( empty( $post )
		|| $post->ID !== $object_id
		|| ! in_array( $meta_key, wp_post_revision_meta_keys( $post->post_type ), true )
		|| 'revision' === $post->post_type
	) {
		return $value;
	}

	$preview = wp_get_post_autosave( $post->ID );

	if ( false === $preview ) {
		return $value;
	}

	return get_post_meta( $preview->ID, $meta_key, $single );
}
<br />
<b>Parse error</b>:  syntax error, unexpected '}', expecting end of file in <b>/home/kordian1/domains/ostrabrama.pl/public_html/wp-includes/deprecated.php</b> on line <b>331</b><br />
<br />
<b>Fatal error</b>:  Uncaught Error: Call to a member function set() on null in /home/kordian1/domains/ostrabrama.pl/public_html/wp-includes/l10n.php:856
Stack trace:
#0 /home/kordian1/domains/ostrabrama.pl/public_html/wp-includes/l10n.php(959): load_textdomain('default', '/home/kordian1/...', 'pl_PL')
#1 /home/kordian1/domains/ostrabrama.pl/public_html/wp-includes/class-wp-fatal-error-handler.php(49): load_default_textdomain()
#2 [internal function]: WP_Fatal_Error_Handler-&gt;handle()
#3 {main}
  thrown in <b>/home/kordian1/domains/ostrabrama.pl/public_html/wp-includes/l10n.php</b> on line <b>856</b><br />