Prevent WordPress MailmanWidget widget to hide after registering your address

If you use the Mailman Widget as an important design element, you might be annoyed by the fact it disappears once you registered your e-mail. A quick hack to this behaviour is to modify ns_widget_mailman.class.php (see comments):

 public function widget ($args, $instance) {
     extract($args);
     // Patch to continue showing block even if registered in this session
     //if ((isset($_COOKIE[$this->id_base . '-' . $this->number]) && $this->hash_mailing_list_id($this->number) == $_COOKIE[$this->id_base . '-' . $this->number]) || false == $this->ns_mm_plugin->get_mailman()) {
     if (false == $this->ns_mm_plugin->get_mailman()) {
         return 0;
     } else {
         $widget = $before_widget . $before_title . $instance['title'] . $after_title;