navigation.inc
function display_output(&$ar,$parameterAr)
{
		...
		$hidden = '';
		if (!$showhidden || $showhidden=='onlyactive')
		{
			$pathIds = '';
			// calculate hidden entries which still should be shown if onlyactive flag is set
			if ($showhidden == 'onlyactive')
			{
				//remove empty string element from the $current_path - happens there sometimes
				$currentPathFiltered = array_filter($current_path);
				if (count($currentPathFiltered))
				{
					//show hidden entries if we're already in (by direct link)
					$pathIds = ' OR id IN ('.implode(',', $currentPathFiltered).')';
				}
			}
			$hidden = ' AND (hidden=0'.$pathIds.')';
		}
		...