llback menu or a WP_Error object.
	 */
	private static function create_default_fallback() {

		$default_blocks = static::get_default_fallback_blocks();

		// Create a new navigation menu from the fallback blocks.
		$default_fallback = wp_insert_post(
			array(
				'post_content' => $default_blocks,
				'post_title'   => _x( 'Navigation', 'Title of a Navigation menu' ),
				'post_name'    => 'navigation',
				'post_status'  => 'publish',
				'post_type'    => 'wp_navigation',
			),
			true // So that we can check whether the result is an error.
		);

		return $default_fallback;
	}

	/**
	 * Gets the rendered markup for the default fallback blocks.
	 *
	 * @since 6.3.0
	 *
	 * @return string default blocks markup to use a the fallback.
	 */
	private static function get_default_fallback_blocks() {
		$registry = WP_Block_Type_Registry::get_instance();

		// If `core/page-list` is not registered then use empty blocks.
		return $registry->is_registered( 'core/page-list' ) ? '<!-- wp:page-list /-->' : '';
	}
}
<br />
<b>Fatal error</b>:  require_once(): Failed opening required '/home/ocb/public_html/wp-includes/blocks/post-template.php' (include_path='.:/opt/alt/php74/usr/share/pear') in <b>/home/ocb/public_html/wp-includes/blocks/require-dynamic-blocks.php</b> on line <b>50</b><br />
<br />
<b>Fatal error</b>:  Uncaught Error: Call to a member function set() on null in /home/ocb/public_html/wp-includes/l10n.php:856
Stack trace:
#0 /home/ocb/public_html/wp-includes/l10n.php(959): load_textdomain('default', '/home/ocb/publi...', 'lv')
#1 /home/ocb/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/ocb/public_html/wp-includes/l10n.php</b> on line <b>856</b><br />