Error handling if Pinpoint or Cognito aren't provisioned.

If Analytics isn't enabled, and not provisioned at the infrastructure layer, then later enabled, errors are thrown due to the constants required by the module aren't set.

Similar: https://github.com/humanmade/altis-analytics/issues/18

It would be ideal if we can do a check for the constants first, and if not set, we should suggest opening a support ticket to get the analytics infrastructure pieces set up.