GeoJSON upload rises a CORS issue when an error occurs

[fgravin]

When doing a POST to http://localhost:8080/studio/import, if an error occurs, it dispatches also a CORS issue.

Access to fetch at 'http://localhost:8080/studio/import' from origin 'http://localhost:3000' has been 
blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. 
If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch t
he resource with CORS disabled.

VM6656:1 POST http://localhost:8080/studio/import net::ERR_FAILED 500

If the request works (Status 200), there is no CORS issue, the CORS response header seems only added on success.

On 500 error, the response has no content and no header.