possible bug in upload component in IE using vaadin 7

Hi,

if you copy the code example of SingeClickUpload in the demo (http://demo.vaadin.com/sampler/#ImmediateUpload) and log the filename and mime type when MyReceiver.receiveUpload() is called, you get “unknown” for both if you use IE 8 and Vaadin 7.
FF and Chrome worked fine for me.