Command-line anonymizer fails if an object doesn't have an AccessionNumber

[Blair Conrad]

Try to anonymize (from the command line) a file that doesn't have an accession number. The anonymization works, but printing the summary fails:

λ  dicognito .                                                                                   
Traceback (most recent call last):                                                               
  File "C:\Program Files\Python37\Scripts\dicognito-script.py", line 11, in <module>             
    load_entry_point('dicognito==0.7.0', 'console_scripts', 'dicognito')()                       
  File "c:\program files\python37\lib\site-packages\dicognito\__main__.py", line 102, in main    
    ConvertedStudy(dataset.AccessionNumber, dataset.PatientID, str(dataset.PatientName))         
  File "c:\program files\python37\lib\site-packages\pydicom\dataset.py", line 556, in __getattr__
    return super(Dataset, self).__getattribute__(name)                                           
AttributeError: 'FileDataset' object has no attribute 'AccessionNumber'