message: ssr: Add guard for health check user agent filter
  Errors are showing up in the logs.
diff: @@ -4,7 +4,8 @@ const fetch = require('node-fetch');
  const Sentry = require('@sentry/node');
  function healthCheckMiddleware(req, res, next) {
  - let isHealthCheck = req.get('user-agent').includes('ELB-HealthChecker');
  + let userAgent = req.get('user-agent') || '';
  + let isHealthCheck = userAgent.includes('ELB-HealthChecker');
  if (isHealthCheck) {
  res.status(200).send('fastboot server is up and running');
  