Undefined index: file_rel_path in import_html_importprocess_form()

After a successful batch import, I can see the following in the logs:

Notice: Undefined index: file_rel_path in import_html_importprocess_form() (line 1196 of /path/to/drupal/sites/all/modules/contrib/import_html/import_html_ui.inc).

Looks like file_rel_path isn't set on this last page of the multi-page form:

      // To keep the state information fresh, (forward/back testing)
      // Make a quiet note of the recently selected checkboxes
      $import_files = (array) $form_state['values']['file_rel_path'];
      $selected_files = array_filter($import_files);
      $form['file_rel_path'] = array(
        '#type' => 'item',
        '#tree' => TRUE,
      );