Delete Specific Format in 3.30

Hi I need to warn you of a bug I found in Calibre 3

I finally got my library structure where I wanted it, and I decided I didn't need duplicate formats.

I removed the formats I don't like, thinking that it would keep the files if they were the only format, which has been the behavior from Calibre previously.

NOW I HAVE A BUNCH OF EMPTY BOOKS!

The remove a specific format function is no longer alerting when you remove all formats from a book.