CheckboxSelectMultiple fails when the queryset is empty

With the following in forms.py
from django.forms.widgets import CheckboxSelectMultiple

forms.ModelMultipleChoiceField(queryset=None, widget=CheckboxSelectMultiple())

The widget fails to load for an emptyqueryset

Thanks

Start with the forms.py example using ModelMultipleChoiceField(queryset=None, widget=CheckboxSelectMultiple()) and trace how CheckboxSelectMultiple handles an empty queryset. Confirm the widget loads successfully for that case without the reported failure.

Written by the indexing model from the issue text.