XML import error about logontracer

[t-tani]

Log

$ python logontracer.py -x dump.xml -z +9
[*] Script start. 2018/08/01 22:02:08
[*] Time zone is 9.
[*] Last record number is 386071.
[*] Start parsing the EVTX file.
[*] Parse the EVTX file dump.xml.
Traceback (most recent call last):
  File "logontracer.py", line 944, in <module>
    main()
  File "logontracer.py", line 939, in main
    parse_evtx(args.xmls)
  File "logontracer.py", line 774, in parse_evtx
    tohours = int((endtime - starttime).total_seconds() / 3600)
TypeError: unsupported operand type(s) for -: 'NoneType' and 'NoneType'

[t-tani]

thank you!