Improve error: no implicit conversion of Symbol into Integer

[arturictus]

The mapper is wrong because it uses from_child and the original has no children, but the error should be better.

mapper

module Worldmate
  class BaobabHotelToModelMapper < HashMap::Base
    after_each HashMap::BlankToNil
    transforms_output proc { |out| out.compact }

    property :name, from: :hotel_name
    properties :phone, :fax
    from_child :address do
      property :address, from: :street
      property :telephone, from: :phone
      property :zip, from: :postal_code
      properties :city, :country_code
    end
  end
end

execution:

original = {
        "id"=>"32ec4be6-2cc2-4acf-ac03-f2d6c1111ee9",
        "name"=>"Hotel Arts Barcelona",
        "address"=>"Carrer de la Marina 19-21",
        "time_zone"=>"Europe/Madrid",
        "state"=>"Barcelona",
        "city"=>"Barcelona",
        "state_code"=>"Barcelona",
        "postal_code"=>"08005",
        "country_code"=>"ES",
        "phone_number"=>"34932211000",
        "latitude"=>41.3870201,
        "longitude"=>2.1960815,
        "website"=>"http://www.ritzcarlton.com/en/hotels/spain/barcelona",
        "chain_code"=>"RZ",
        "sabre_id"=>"27456",
        "google_id"=>"ChIJG11mEw-jpBIRVUCfp2u8Pv8",
        "amadeus_id"=>"RZBCNBAR",
        "fcm_id"=>"139802"
      }

[arturictus]

same as #30, I close this one.