Flatproduct doesn't have a product_class_id anymore
Flatproduct doesn't have a product_class_id anymore

We sometimes pass a flatproduct into this place, and that doesn't have a
product_class_id anymore.

This is a quick fix for
https://www.sentry.machtfitdev.de/machtfit/machtfit-20/issues/776/ done before I
fully understand why this code and error was triggered only today and not
earlier.

machtfit/django-oscar,machtfit/django-oscar,machtfit/django-oscar