Fix Resumable.js response code on test request

[nerg4l]

test request documentation of Resumable.js: https://github.com/23/resumable.js#handling-get-or-test-requests

If the request returns anything else, the chunk will be uploaded in the standard fashion. (It is recommended to return 204 No Content in these cases if possible to avoid unwarranted notices in browser consoles.)

Before the library throw a NotFoundHttpException when the chunk of the file was missing. Now it is returning a 204 No Content response as suggested by the documentation.