Minor improvement to changed_download_progress()

Minor improvement to changed_download_progress()

I checked WebKit's source code: webkit_download_get_destination_uri()
never returns NULL in lariza. It's because we set the destination URI in
the signal handler for the download request.

If g_filename_from_uri() really returned NULL for some reason, then it'd
be just plain wrong to announce the "suggested file name", because we
might be saving the download ... somewhere else. I doubt this function
ever returns NULL in lariza, though, but you never know.

So, now, the download manager will correctly show the URI if the
destination URI is "unknown".