Try this search and hover on the empty tag the sidebar shows. You can also make your own query; try
The empty tag really shouldn't exist/be shown. If you search
[*] it seems to recognize that's not a real search. It only lets you search the empty tag if you search
[tag] -[*] or if you just construct a URL like I have above.
Hovering on the empty tag clears the page and presents this:
And if you hover over it the page turns completely blank.