Safe check for model_field.null (compatible with ME pre-0.9.0)
Safe check for model_field.null (compatible with ME pre-0.9.0)

BurkovBA/django-rest-framework-mongoengine,arpitgoyalhtmedia/django-rest-framework-mongoengine,nicolascine/django-rest-framework-mongoengine,foundi/django-rest-framework-mongoengine,umutbozkurt/django-rest-framework-mongoengine,arpitgoyaiitkgp/django-rest-framework-mongoengine,optik/django-rest-framework-mongoengine,pombredanne/django-rest-framework-mongoengine