Radius tools crashing

when wortking thru the manual to get details on radius users.

 univention-radius-check-access --username=janek

Traceback (most recent call last):
  File "/usr/bin/univention-radius-check-access", line 66, in <module>
  File "/usr/bin/univention-radius-check-access", line 52, in main
    networkAccess = NetworkAccess(options.username, options.station_id, loglevel=4)
  File "/usr/lib/python3/dist-packages/univention/radius/networkaccess.py", line 103, in __init__
    self.mac_address = decode_stationId(stationId)
  File "/usr/lib/python3/dist-packages/univention/radius/utils.py", line 39, in decode_stationId
    norm = "".join(c for c in stationId.lower() if c in "0123456789abcdef")
AttributeError: 'NoneType' object has no attribute 'lower'