AttributeError: 'NoneType' object has no attribute 'choices'

[Deleted user]

I get an attribute error like this:

AttributeError
AttributeError: 'NoneType' object has no attribute 'choices'

Traceback (most recent call last)
File "/Users/tianyu/.virtualenvs/dealpick/lib/python2.7/site-packages/flask/app.py", line 1836, in call
return self.wsgi_app(environ, start_response)
File "/Users/tianyu/.virtualenvs/dealpick/lib/python2.7/site-packages/flask/app.py", line 1820, in wsgi_app
response = self.make_response(self.handle_exception(e))
File "/Users/tianyu/.virtualenvs/dealpick/lib/python2.7/site-packages/flask/app.py", line 1403, in handle_exception
reraise(exc_type, exc_value, tb)
File "/Users/tianyu/.virtualenvs/dealpick/lib/python2.7/site-packages/flask/app.py", line 1817, in wsgi_app
response = self.full_dispatch_request()
File "/Users/tianyu/.virtualenvs/dealpick/lib/python2.7/site-packages/flask/app.py", line 1477, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/Users/tianyu/.virtualenvs/dealpick/lib/python2.7/site-packages/flask/app.py", line 1381, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "/Users/tianyu/.virtualenvs/dealpick/lib/python2.7/site-packages/flask/app.py", line 1475, in full_dispatch_request
rv = self.dispatch_request()
File "/Users/tianyu/.virtualenvs/dealpick/lib/python2.7/site-packages/flask/app.py", line 1461, in dispatch_request
return self.view_functionsrule.endpoint
File "/Users/tianyu/.virtualenvs/dealpick/lib/python2.7/site-packages/flask_superadmin/base.py", line 36, in inner
return f(self, _args, *_kwargs)
File "/Users/tianyu/.virtualenvs/dealpick/lib/python2.7/site-packages/flask_superadmin/base.py", line 36, in inner
return f(self, _args, *_kwargs)
File "/Users/tianyu/.virtualenvs/dealpick/lib/python2.7/site-packages/flask_superadmin/base.py", line 36, in inner
return f(self, _args, *_kwargs)
File "/Users/tianyu/.virtualenvs/dealpick/lib/python2.7/site-packages/flask_superadmin/model/base.py", line 278, in edit
Form = self.get_form(include_readonly=request.method == 'GET')
File "/Users/tianyu/.virtualenvs/dealpick/lib/python2.7/site-packages/flask_superadmin/model/base.py", line 132, in get_form
converter=converter)
File "/Users/tianyu/.virtualenvs/dealpick/lib/python2.7/site-packages/flask_superadmin/model/backends/mongoengine/orm.py", line 300, in model_form
field_dict = model_fields(model, only, exclude, field_args, converter)
File "/Users/tianyu/.virtualenvs/dealpick/lib/python2.7/site-packages/flask_superadmin/model/backends/mongoengine/orm.py", line 223, in model_fields
field = converter.convert(model, model_field, field_args.get(name))
File "/Users/tianyu/.virtualenvs/dealpick/lib/python2.7/site-packages/flask_superadmin/model/base.py", line 17, in convert
field = super(AdminModelConverter, self).convert(_args, *_kwargs)
File "/Users/tianyu/.virtualenvs/dealpick/lib/python2.7/site-packages/flask_superadmin/model/backends/mongoengine/orm.py", line 72, in convert
return self.converters[ftype](model, field, kwargs)
File "/Users/tianyu/.virtualenvs/dealpick/lib/python2.7/site-packages/flask_superadmin/model/backends/mongoengine/orm.py", line 155, in conv_List
if field.field.choices:
AttributeError: 'NoneType' object has no attribute 'choices'

I do not know how to fix it,can u help me ?
This is my model used mongoengine v0.8.1:

class Deal(Document, IncludeUniqueIDField):
    site         = StringField()
    key          = StringField()
    url          = StringField()

    title        = StringField()
    description  = StringField()
    price        = StringField()
    list_price   = StringField()
    image        = ListField()

    shipping     = StringField()
    manufacturer = StringField()
    expired      = BooleanField()
    is_hot       = BooleanField()

    score        =   FloatField(default=0)
    posted_at    =   DateTimeField()
    created_at   =   DateTimeField(default=datetime.utcnow)
    updated_at   =   DateTimeField()
    ublished_at  =   DateTimeField()

    visible      =   BooleanField(default=True)

    meta = {
        'indexes': [('site', 'key')],
    }

and the flask-superadmin is latest version.