fix delete() use of old user.message_set on OSError
fix delete() use of old user.message_set on OSError

wardi/django-filebrowser-no-grappelli,agushuley/gu-django-filebrowser-no-grappelli,agushuley/gu-django-filebrowser-no-grappelli,aladdinwang/django-filebrowser-no-grappelli,MagicSolutions/django-filebrowser-no-grappelli,MagicSolutions/django-filebrowser-no-grappelli,wardi/django-filebrowser-no-grappelli,aladdinwang/django-filebrowser-no-grappelli,wardi/django-filebrowser-no-grappelli,agushuley/gu-django-filebrowser-no-grappelli,aladdinwang/django-filebrowser-no-grappelli,wardi/django-filebrowser-no-grappelli,MagicSolutions/django-filebrowser-no-grappelli,agushuley/gu-django-filebrowser-no-grappelli