Notice: Undefined index: format în nivo_slider_slider()

I get the following php notice with this module installed:

Notice: Undefined index: format în nivo_slider_slider() (linia 94 din /data/drupal/sites7/burlacutrans.com/modules/nivo_slider/slider.inc).

I don't set any description for image because I don't want captions so I think that the following function should look like this:

function nivo_slider_slider() {
...

  foreach ($visible_slides as $slide => $settings) {
    // Create a variable to hold the slide description
    $description = '';

//OUTPUT ONLY FOR IMAGE WITH DESCRIPTIONS
    if(!is_null($settings['description']['value'])) {
      // Set the slide description directly when using plain text otherwise create an
      // HTML caption

//CHECK IF 'FORMAT' IS SET
      if (isset($settings['description']['format']) && $settings['description']['format'] == 'plain_text') {
        $description = $settings['description']['value'];
      }
      else {
        ...
      }
    }
...
}