DataCite parser fails with affiliations that are None

[marblestation]

{"asctime": "2019-01-07T22:01:45.260Z", 
"levelname": "ERROR", 
"processName": "ForkPoolWorker-3", 
"message": "Failed parsing", 
"exc_info": "Traceback (most recent call last):\n
  File \"/app/ADSCitationCapture/doi.py\", line 208, in _parse_metadata_zenodo_doi\n
    parsed_metadata = dc.parse(raw_metadata)\n  File \"/usr/local/lib/python2.7/dist-packages/pyingest/parsers/datacite.py\", line 168, in parse\n
    aaffils.append(aff.strip())\n
AttributeError: 'NoneType' object has no attribute 'strip'", 
"timestamp": "2019-01-07T22:01:45.260Z", 
"hostname": "adsvm05"}