[Plugin: Rating-Widget] Warning: array_key_exists(): The first argument should be either a string or

I have installed Rating-Widget Plugin 1.4.6 on WordPress 3.4.1, but when I active the Rating Widger Top Rated, I have this error:

Warning: array_key_exists(): The first argument should be either a string or an integer in /web/htdocs/www.***.it/wp-includes/cache.php on line 537

The problem is into file rating-widget.php to line 3757, I have this:

case "comments":
     $id = RatingWidgetPlugin::Urid2CommentId($urid);
     $comment = get_comment($id);
     $title = trim(strip_tags($comment->comment_content));
     $permalink = get_permalink($comment->comment_post_ID) . '#comment-' . $comment->comment_ID;
  break;

and I have solved the error adding “(int)” function on $id …

case "comments":
     $id = (int)RatingWidgetPlugin::Urid2CommentId($urid);
     $comment = get_comment($id);
     $title = trim(strip_tags($comment->comment_content));
     $permalink = get_permalink($comment->comment_post_ID) . '#comment-' . $comment->comment_ID;
  break;

http://ww.wp.xz.cn/extend/plugins/rating-widget/