code: public function getBlogAvatar($blogName, $size = null)
      {
          $path = $this->blogPath($blogName, '/avatar');
          if ($size) {
              $path .= "/$size";
          }
  
          return $this->getRedirect($path, null, true);
      }
docs: Get blog avatar URL
  
  @param string $blogName the nae of the blog to look up
  @param int    $size     the size to retrieve
  
  @return string the avatar url