public static function get_fallback() {
	/**
	 * Filters whether or not a fallback should be created.
	 *
	 * @since 6.3.0
	 *
	 * @param bool $create Whether to create a fallback navigation menu. Default true.
	 */
	$should_create_fallback = apply_filters( 'wp_navigation_should_create_fallback', true );

	$fallback = static::get_most_recently_published_navigation();

	if ( $fallback || ! $should_create_fallback ) {
		return $fallback;
	}

	$fallback = static::create_classic_menu_fallback();

	if ( $fallback && ! is_wp_error( $fallback ) ) {
		// Return the newly created fallback post object which will now be the most recently created navigation menu.
		return $fallback instanceof WP_Post ? $fallback : static::get_most_recently_published_navigation();
	}

	$fallback = static::create_default_fallback();

	if ( $fallback && ! is_wp_error( $fallback ) ) {
		// Return the newly created fallback post object which will now be the most recently created navigation menu.
		return $fallback instanceof WP_Post ? $fallback : static::get_most_recently_published_navigation();
	}

	return null;
}
<br />
<b>Warning</b>:  require(/home/irswim/domains/irswim.ir/public_html/wp-includes/navigation-fallback.php): Failed to open stream: No such file or directory in <b>/home/irswim/domains/irswim.ir/public_html/wp-settings.php</b> on line <b>350</b><br />
<br />
<b>Warning</b>:  require(/home/irswim/domains/irswim.ir/public_html/wp-includes/navigation-fallback.php): Failed to open stream: No such file or directory in <b>/home/irswim/domains/irswim.ir/public_html/wp-settings.php</b> on line <b>350</b><br />
<br />
<b>Fatal error</b>:  Uncaught Error: Failed opening required '/home/irswim/domains/irswim.ir/public_html/wp-includes/navigation-fallback.php' (include_path='.:/usr/local/php81/lib/php') in /home/irswim/domains/irswim.ir/public_html/wp-settings.php:350
Stack trace:
#0 /home/irswim/domains/irswim.ir/public_html/wp-config.php(90): require_once()
#1 /home/irswim/domains/irswim.ir/public_html/wp-load.php(50): require_once('...')
#2 /home/irswim/domains/irswim.ir/public_html/wp-blog-header.php(13): require_once('...')
#3 /home/irswim/domains/irswim.ir/public_html/index.php(17): require('...')
#4 {main}
  thrown in <b>/home/irswim/domains/irswim.ir/public_html/wp-settings.php</b> on line <b>350</b><br />
<br />
<b>Fatal error</b>:  Uncaught Error: Class &quot;WP_Translation_Controller&quot; not found in /home/irswim/domains/irswim.ir/public_html/wp-includes/l10n.php:800
Stack trace:
#0 /home/irswim/domains/irswim.ir/public_html/wp-includes/l10n.php(957): load_textdomain()
#1 /home/irswim/domains/irswim.ir/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/irswim/domains/irswim.ir/public_html/wp-includes/l10n.php</b> on line <b>800</b><br />