TypeError: %d format: a number is required, not NoneType

[rom1504]

I'm getting this :

Traceback (most recent call last):
  File "./sync_daemon.py", line 364, in run_with_except_hook
    run_original(*args2, **kwargs2)
  File "/usr/lib/python3.7/threading.py", line 1166, in run
    self.function(*self.args, **self.kwargs)
  File "./sync_daemon.py", line 166, in sync_to_trakt
    log.debug('sync_to_trakt(%s, %d, %s, %s, %d, %d, %s)' % (is_paused, playback_position, working_dir, path, duration, start_time, mpv_closed))
TypeError: %d format: a number is required, not NoneType

What could be the error ?