Kwargs should contain 'queryset' when child is a FormSet on edition

[decolens]

When using MultiForm for editing models (= putting 'instance' in the kwargs), if one or several of the forms contained inside the MultiForm are FormSet, a TypeError with message "init() got an unexpected keyword argument 'instance'" is raised.
I think this error is due to the "fkwargs = kwargs.copy()" line in the "get_form_args_kwargs" method of multiform.py. If the MultiForm kwargs are copied for any of the child, they will all contain the 'instance' argument, instead of the 'queryset' needed for FormSet.

[decolens]

I have added a possible fix for this bug. See lines 184-187 in get_form_args_kwargs of MultiModelForm. For that to work I needed to add "from django.db.models.query import QuerySet" (see line 18 in the imports)
multiform_master.txt