Issue with DragAndDropWrapper to initiate download.

Vaadin 6 / 7 / 8
1

Hello,

When I try the demo: “DragAndDropWrapper to initiate download”:
(http://demo.vaadin.com/sampler/#ui/data-input/other/drop-items)
and I drop just one file ; I can notice that the application “falls”
Have you an idea ?

Thanks