Made `render_field()` return an empty SafeString when `field` is `None`. (#1273)
Made `render_field()` return an empty SafeString when `field` is `None`. (#1273)

Previously a `str` was returned if `field` is None. The other code paths in this function all return `SafeString`, therefore this change makes the return type consistent for the whole function.
django-crispy-forms/django-crispy-forms,django-crispy-forms/django-crispy-forms