Return error of API client instead of sending null when exporting

[philipperobertgh]

When we export data from RAO to prevention, sometimes a null reference is sent instead of the real error of the API.

Ex. : Use ApiClientTester without api service running
when api service is not running the BaseSecureService send null value in ExecuteAsync Method.

We should return:

• 404 or 500 when there's a problem with the api service

More:
When the loggin doesn't succeed the api return

Should we build some built-in message and force api to return http error code or we display the message as is it ?