false cannot be mapped to a known ISO language code

[andrecedik]

We're automatically booking the advance_notice service, if a user has selected to use email notifications by the carrier. If the users wants to send a shipment to an address in a country, where we haven't specified the ISO language code, the method for getting the correct language code currently returns false.

"additional_services": [{
  "name": "advance_notice",
  "properties": {
    "email": "info@shipcloud.io",
    "language": false
  }
}]

We should catch this.