Fix: use require instead include_once

htdocs/core/lib/files.lib.php

@@ -59,7 +59,7 @@ function dol_dir_list($path, $types="all", $recursive=0, $filter="", $excludefil
 	{
 		if (! class_exists('HookManager')) {
 			// Initialize technical object to manage hooks of thirdparties. Note that conf->hooks_modules contains array array
-			include_once DOL_DOCUMENT_ROOT.'/core/class/hookmanager.class.php';
+			require DOL_DOCUMENT_ROOT.'/core/class/hookmanager.class.php';
 			$hookmanager=new HookManager($db);
 		}
 	}