Traceback (most recent call last):
  File "/home/stepan7/.local/lib/python3.6/site-packages/flask/app.py", line 2464, in __call__
    return self.wsgi_app(environ, start_response)
  File "/home/stepan7/.local/lib/python3.6/site-packages/flask/app.py", line 2450, in wsgi_app
    response = self.handle_exception(e)
  File "/home/stepan7/.local/lib/python3.6/site-packages/flask/app.py", line 1867, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "/home/stepan7/.local/lib/python3.6/site-packages/flask/_compat.py", line 39, in reraise
    raise value
  File "/home/stepan7/.local/lib/python3.6/site-packages/flask/app.py", line 2447, in wsgi_app
    response = self.full_dispatch_request()
  File "/home/stepan7/.local/lib/python3.6/site-packages/flask/app.py", line 1952, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/home/stepan7/.local/lib/python3.6/site-packages/flask/app.py", line 1821, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/home/stepan7/.local/lib/python3.6/site-packages/flask/_compat.py", line 39, in reraise
    raise value
  File "/home/stepan7/.local/lib/python3.6/site-packages/flask/app.py", line 1950, in full_dispatch_request
    rv = self.dispatch_request()
  File "/home/stepan7/.local/lib/python3.6/site-packages/flask/app.py", line 1936, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/home/stepan7/.local/lib/python3.6/site-packages/flask_discord/utils.py", line 22, in wrapper
    return view(*args, **kwargs)
  File "/home/stepan7/PycharmProjects/mailer/app.py", line 43, in store_mailing
    print(form.validate(), form.errors)
  File "/home/stepan7/.local/lib/python3.6/site-packages/wtforms/form.py", line 318, in validate
    return super(Form, self).validate(extra)
  File "/home/stepan7/.local/lib/python3.6/site-packages/wtforms/form.py", line 150, in validate
    if not field.validate(self, extra):
  File "/home/stepan7/.local/lib/python3.6/site-packages/wtforms/fields/core.py", line 215, in validate
    self.pre_validate(form)
  File "/home/stepan7/.local/lib/python3.6/site-packages/wtforms/fields/core.py", line 509, in pre_validate
    for v, _ in self.choices:
TypeError: 'NoneType' object is not iterable