Notice: Undefined property: stdClass::$error in boost_requirements() (line 105) of boost.install

Fix: (patch below)

      if (BOOST_CRAWL_ON_CRON) {
        $crawler_response = drupal_http_request(BOOST_CRAWLER_SELF . '&test=1', array(), 'GET', NULL, 10);
        $crawler_code = $crawler_response->code;
+        if(isset($crawler_response->error)) {            // Stop 'PHP - warning - Undefined property: stdClass::$error'
          $crawler_error = $crawler_response->error;
+        }
      }
      $robots = drupal_http_request('http://' . check_plain($_SERVER['HTTP_HOST']) . '/robots.txt');