Ohhhh... you are doing this on the Manage Authors dialog. Hmmmm... now that isn't where I was thinking your were
. And yes to me that sounds like a bug in calibre, I'm sure Kovid or chaley can confirm it. It sounds like the books are being left associated with your author which you have now set to "blank", rather than being set to the "Unknown" author.
Because if you then try to hit F2 on the author for a specific book (in the library view), and hit Enter, the author becomes "Unknown" as I would expect.
So like I say, think you have found a calibre bug. I should also add some protection in the next version of this plugin to handle this situation better - I hadn't found a way to make an author blank so I assumed it was not possible, however you proved that theory wrong
