Invalid behaviour on HTTP 400 error responses

[cordawyn]

When using a SPARQL endpoint for document location, RDF Editor pops up an authentication dialog in case of HTTP 400 error response from the endpoint. For example, RDF4J server responds with HTTP 400 error in case of SPARQL syntax errors in the request (with the body containing the explanation/error details).

I suspect that RDF Editor might show the authentication dialog on any 4xx errors, while it should do so only in case of 401. Perhaps, when encountering other 4xx errors, it should show the error pop-up (as it already does), but with the response body contents, to give users some idea why the error occurred.