Swimbot Error

Traceback (most recent call last):
  File "C:\Users\swimm\AppData\Local\Programs\Python\Python37\lib\site-packages\discord\ext\commands\core.py", line 85, in wrapped
    ret = await coro(*args, **kwargs)
  File "c:\Users\swimm\OneDrive\Desktop\Swimbot\premium.py", line 41, in clanpromo
    if not ctx.invoked_subcommand: raise commands.MissingRequiredArgument(None)
  File "C:\Users\swimm\AppData\Local\Programs\Python\Python37\lib\site-packages\discord\ext\commands\errors.py", line 145, in __init__
    super().__init__('{0.name} is a required argument that is missing.'.format(param))
AttributeError: 'NoneType' object has no attribute 'name'