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 130, in channel
    if '#' not in tag: tag = f'#{tag}'
TypeError: argument of type 'NoneType' is not iterable