Bug Moving the entire library

Hi,
I have just copied and deleted with the appropriate menu option the whole library. Now it is empy.
The library now just show in the right side the cover of the last book, its authors and description. If I click on the "Format" I have the following:

calibre, version 0.9.9
ERRORE: Eccezione non gestita: <b>TypeError</b>:'NoneType' object has no attribute '__getitem__'

Traceback (most recent call last):
File "site-packages\calibre\gui2\actions\view.py", line 98, in view_format_by_id
File "site-packages\calibre\library\database2.py", line 1334, in format_abspath
File "site-packages\calibre\library\database2.py", line 572, in path
TypeError: 'NoneType' object has no attribute '__getitem__'