Необработанное исключение при десериализации пустого поля с помощью json_serializable

Question

Я получаю эту ошибку при попытке десериализации json, она выдает ошибку при разборе пустого поля. [ { "entity": "1", "name_alias": "NAME", "address": "ADDRESS", "zip": null, "town": "TOWN", }]

Вот часть кода, генерирующая исключение:

      CustomerListResp _$CustomerListRespFromJson(Map<String, dynamic> json) {
   return CustomerListResp()
    ..customers = (json['customers'] as List<dynamic>)
        .map((e) => Customer.fromJson((e as Map<String, dynamic>).map(
              (k, e) => MapEntry(k, e as Object), // throw exception when parsing the zip field
            )))
        .toList();
}

      json_serializable: ^4.0.2
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