Remove warning about missing file from parserstress test

There is no dummy.qml, so trying to find it will cause a warning
and return an empty string. Since the url is optional anyway and
apparently not relevant to this test, just use empty QUrl directly.

Change-Id: I11ba742dedccd6bdea226f680aa57c957afc7dc7
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@nokia.com>

tests/auto/qml/parserstress/tst_parserstress.cpp

@@ -128,8 +128,7 @@ void tst_parserstress::ecmascript()
 
     QQmlComponent component(&engine);
 
-    QString dummyFile = QFINDTESTDATA("dummy.qml");
-    component.setData(qmlData, QUrl::fromLocalFile(dummyFile));
+    component.setData(qmlData, QUrl());
 
     QFileInfo info(file);