Wot: crash on membership status

ji_emme_test_2 (39Fno…) from block #172594-0000418C…
received 4 and sent 2/100 certifications:
|  received_expire  |      received       |  sent  |  sent_expire  |
|-------------------+---------------------+--------+---------------|
|    2018-12-20     |   scanlegentil ✔    | guwop  |  2018-12-10   |
|    2019-03-06     |    Vincentest ✔     |  h30x  |  2018-12-18   |
|    2019-03-06     |        vit ✔        |        |               |
|    2019-03-06     | matograine-G1Test ✔ |        |               |

member: False
Traceback (most recent call last):
  File "/home/moul/projects/silkaj/bin/silkaj", line 13, in <module>
    manage_cmd()
  File "/home/moul/projects/silkaj/silkaj/cli_tools.py", line 176, in manage_cmd
    received_sent_certifications(cli_args.subsubcmd)
  File "/home/moul/projects/silkaj/silkaj/wot.py", line 75, in received_sent_certifications
    membership_status(certifications, certs, pubkey, req)
  File "/home/moul/projects/silkaj/silkaj/wot.py", line 101, in membership_status
    convert_time(req["revoked_on"]),
TypeError: convert_time() missing 1 required positional argument: 'kind'