Product with variants: Product-Property-Values can't be updated

[prinzdezibel]

Reproduct:

• Create a product with variants
• Create properties (local or global), does not matter
• Change the property values of a specific variant and hit save

Expected:

• The changed property value should be saved and displayed when page is reloaded

Result:

• The original property value is displayed in select box, not the changed value.

[Zagrebelin]

Fixed in this commit. I don't know how to make pull-request from single commit.