message: skip user fields that is either undefined or null
diff: @@ -12,6 +12,11 @@ module.exports = {
  let custom_claims = {};
  USER_FIELDS.forEach(user_field => {
  +
  + if (typeof user[user_field] === undefined || user[user_field] === null) {
  + return null;
  + }
  +
  custom_claims['x-hasura-' + user_field.replace('_', '-')] = user[user_field] && user[user_field].toString();
  });
  