Page class Leader board error

I get this error: Notice: Undefined variable: pageclass in /home/websitename/public_html/modules/mod_leaderboard/mod_leaderboard.php on line 18

Here is the line of code in question:
$document->addStyleSheet(JURI::base(true).'/modules/mod_leaderboard/assets/css/leaders_styles' . $pageclass . '.css');

The error doesn't show always, if I refresh the page, sometimes it will not show any error. Right now I have turned the module off, because of the error. I am using the latest version.