[QtQuick] XmlHttpRequest status is "lost" (becomes 0) in readyState 3->4 transition for PUT requests yielding response with custom HTTP status

var xhr = new XMLHttpRequest(),
    method = 'PUT',
    baseUrl = 'http://localhost:5984/data/', // REST entry point to a CouchDB database
    newCouchDocumentId = '331ed149-af1a-4979-bd2e-0186b8738c5f', // random client-generated UUID
    url = baseUrl + newCouchDocumentId,
    async = true,
    couchDocumentPayload = '{"description":"Hello World"}'; // The body of the document to be created

xhr.open(method, url, async);
xhr.onreadystatechange = function() {
    console.log('readyState:', xhr.readyState, 'status:', xhr.status);
}
xhr.send(couchDocumentPayload)

// Below is the QML console log after clicking the button twice.

// On first click, CouchDB successfully creates the requested resource,
// and returns HTTP status code 201 ("Created"):
// qml: readyState: 2 status: 201
// qml: readyState: 3 status: 201
// qml: readyState: 4 status: 201

// On second click, as expected, CouchDB refuses creation, because
// our previously-created resource is already there at the same URI,
// and returns a CouchDB-specific error code 409 ("Conflict").
// But rather than ending up at {readyState=4, status=409},
// here is what we see:
// qml: readyState: 2 status: 409
// qml: readyState: 3 status: 409
// qml: readyState: 4 status: 0