The Folder dropdown is empty and the Upload button doesn't do anything, but no message is presented to the user regarding why nothing happens when he clicks upload.
Edit from Charlie: this is a change of behavior (regression?) post-1.7.6. In 1.7.6, it wasn't good practice, but XNAT would let you upload files like this under a "NO LABEL" option. It looks like it was changed intentionally in 1.7.7.