No feedback when oC location URL is malformed

[Apophenia]

When a PUT request to a malformed URL fails, the browser does not log a response with a status code, and the asynchronous call never returns. For this reason, the promise returned by the WebDAV service's "put" method is neither resolved nor rejected, but hangs indefinitely.

If a user inputs an invalid oC location which "looks" like a correct URL, but refuses connections or returns a 404, the app has no means to provide feedback when the PUT requests fail (because the function calling it is not notified of this error). In this case, the result is simply an NS_ERROR_FILE_NOT_FOUND error. Before the app is ready for general use, it will be necessary to introduce something into the upload process that checks to make sure the remote location is receiving PUT requests.