I seem to have broken this plugin.
Here are the steps that caused the problem.
1. Load a PDF into Calibre.
2. Convert the PDF to Mobi.
3. Add the Mobi to the Book Sync List.
4. Remove the PDF from Calibre. (Ops.. this removes the Mobi book too).
5. Look at the Book Sync list.
Then you get:
TypeError: 'NoneType' object is not subscriptable
I've tried uninstalling the plugin and reinstalling. It's still broke. Is there any way to delete the sync list (there were two other books on the list before I hosed things up)? I suspect that the list is corrupt since it contains an entry to a book that I removed from Calibre. When I re-added the book, Book Sync was still broke.