Qual: Missing global declaration

htdocs/core/modules/export/export_excel2007.modules.php

@@ -80,6 +80,8 @@ class ExportExcel2007 extends ExportExcel
      */
 	function close_file()
 	{
+		global $conf;
+
 		if (! empty($conf->global->MAIN_USE_PHP_WRITEEXCEL))
     	{
 	        $this->workbook->close();