GX-Entwicklung

To create a new option value you have to provide a product model.
Since this isn't the case for regular products, this also shouldn't be the case for option values.

Steps to reproduce:

1. Create a new option value for an option.
2. Fill out the required fields except the one for the "Product model".
3. Save the option value.

Expected result:
The product option is saved without a product model.

Actual result:
The product model can't be saved, if no product model is entered.