Hi I have this error when use the module nivoslider, what I can do ? Thank you

Notice: Undefined variable: folders in C:\wamp\www\fina\modules\mod_nivoslider\tmpl\default.php on line 15
Call Stack
# Time Memory Function Location
1 0.0009 697240 {main}( ) ..\index.php:0
2 1.1128 14408760 JSite->render( ) ..\index.php:48
3 1.1998 14736752 JDocumentHTML->render( ) ..\application.php:272
4 1.1998 14736752 JDocumentHTML->_renderTemplate( ) ..\html.php:433
5 1.2408 14938448 JDocumentHTML->getBuffer( ) ..\html.php:655
6 1.2434 14952576 JDocumentRendererModules->render( ) ..\html.php:371
7 1.2436 14953560 JDocumentRendererModule->render( ) ..\modules.php:39
8 1.2445 14959752 JModuleHelper::renderModule( ) ..\module.php:106
9 1.2503 15038800 include( 'C:\wamp\www\fina\modules\mod_nivoslider\mod_nivoslider.php' ) ..\helper.php:175
10 1.2836 15134824 require( 'C:\wamp\www\fina\modules\mod_nivoslider\tmpl\default.php' ) ..\mod_nivoslider.php:2