Create empty queryset by default in django form fields

@radtek's comment should be an answer as it is useful in similar scenarios but with different approach than the accepted answer.

If your queryset changes with the url in your view.

I am extending the answer with example as I used:

def my_view(request):
    ...
    form = YourForm(initial={'field1':value1, 'field2':value2})
    form.fields['field3'].queryset = YourModel.objects.filter('foo'=bar)

You can have an empty queryset by doing this:

MyModel.objects.none()

Although i don't know how are you going to use that form, you can put that as your field's queryset in order to get what you need...

You can find more information here