Gravatar头像被墙之后，Typecho头像就显示不出来了
解决方案如下：

public function gravatar($size = 32, $default = NULL)
    {
        if ($this->options->commentsAvatar && 'comment' == $this->type) {
            $rating = $this->options->commentsAvatarRating;
            $this->pluginHandle(__CLASS__)->trigger($plugged)->gravatar($size, $rating, $default, $this);
            if (!$plugged) {
                //$url = Typecho_Common::gravatarUrl($this->mail, $size, $rating, $default, $this->request->isSecure());
                $mailHash = NULL;
                if (!empty($this->mail)) {
                $mailHash = md5(strtolower($this->mail));
                }
                $url = 'https://secure.gravatar.com/avatar/';
                if (!empty($this->mail)) {$url .= $mailHash;}
                $url .= '?s=' . $size;
                $url .= '&r=' . $rating;
                $url .= '&d=' . $default;
                echo '<img class="avatar" src="' . $url . '" alt="' .
                $this->author . '" width="' . $size . '" height="' . $size . '" />';
            }
        }
    }