In reply to Fultonius:
Ooo that's a good one - you can still delete buttresses without names but you need to look at the HTML to find the buttress id.
If you're on Firefox then right click on the blank buttress, choose "inspect element" and look for something like id="btr_20339" (which is a blank one I've just created in one of my crags...)
then you can go to
http://www.ukclimbing.com/logbook/modbuttress.php?id=xxxxxx (where xxxxxx is 20339 or similar) and delete it.
Edit - I've just removed the test one I made and it does work, but you need to be on the "Moderate" page to find the id
Post edited at 16:57