crash in config dialog (created on behalf of @twentw)

[GRiker]

http://www.mobileread.com/forums/showpost.php?p=2625461&postcount=27

TypeError:'NoneType' object has no attribute '_getitem'
calibre 1.3 isfrozen: True is64bit: False
Windows-7-6.1.7601.SP1 Windows ('32bit', 'WindowsPE')
('Windows','7','6.1.7601')
Python 2.7.5
Windows: ('7',6.1.7601', 'SP1', Multiprocessor Free')
Traceback (most recent call last):
File "calibre_plugins.mar5vin_manager.config", line 680, in run
File "calibre_plugins.mar5vin_manager.config", line 699, in
find_all_annotated_books
TypeError: 'NoneType' object has no attribute '_getitem'