Fixes bcit-ci#6175 fix $this->uri->ruri_string() generates in PHP 8.1

* it coplements prevous commit and related to
  commit ad1a307
  is not the proper way but compatible with
  bcit-ci/CodeIgniter#6117
  and solves
  bcit-ci/CodeIgniter#6120

appsys/core/URI.php

@@ -645,7 +645,7 @@ public function uri_string()
 	 */
 	public function ruri_string()
 	{
-		return ltrim(load_class('Router', 'core')->directory, '/').implode('/', $this->rsegments);
+		return ltrim((string) load_class('Router', 'core')->directory, '/').implode('/', $this->rsegments);
 	}
 
 }