Forces save on empty inlines with non-empty sub-inlines.
Forces save on empty inlines with non-empty sub-inlines.

Fixes #2.

end0/django-super-inlines,BertrandBordage/django-super-inlines,end0/django-super-inlines,BertrandBordage/django-super-inlines,BertrandBordage/django-super-inlines,end0/django-super-inlines