Crash when deleting Variations when ArrangeBy changed from Category to Name...

[CartBlanche]

Steps to reproduce:
0. Make sure ArrangeBy is in Category mode.

1. Create a Variation
2. Switch ArrangeBy to Name mode
3. Delete the Variation that was created.

What happens:
Argument Null Exception is thrown within OnRemoveVariantClicked. parent is null.

Expected behaviour:
No crash and selected Variation is deleted.