pycsw import error on empty keywords at mcf

[pvgenuchten]

caused by sequence:

keywords:
  default:
    keywords: 
    - ''

TypeError: sequence item 0: expected str instance, NoneType found
Could not parse "/builds/7sRQ5izy/0/isric/lsc-hubs/rwanda-hub/portals/RW/mgwalsh-RwaSIS/WP20.xml" as an XML record
Traceback (most recent call last):
  File "/home/pycsw/pycsw/pycsw/core/admin.py", line 373, in load_records
    record = metadata.parse_record(context, metadata_record, repo)
  File "/home/pycsw/pycsw/pycsw/core/metadata.py", line 119, in parse_record
    return _parse_metadata(context, repos, record)
  File "/home/pycsw/pycsw/pycsw/core/metadata.py", line 149, in _parse_metadata
    return [_parse_iso(context, repos, exml)]
  File "/home/pycsw/pycsw/pycsw/core/metadata.py", line 1429, in _parse_iso
    _set(context, recobj, 'pycsw:Keywords', ','.join([k.name for k in all_keywords]))