How to unset a reference field?

Ok, pretty sure NULL failed because of EntityMetadataWrapper::validate() checking the $value via entity_property_verify_data_type(). Since the field's type should be commerce_product, I'm guessing it's failing here:

    // entity.property.inc line 225:
    default:
    case 'struct':
      return is_object($data) || is_array($data);

Ok, so this patch does work as I expected it to, but it doesn't actually let you unset a field value like I was thinking it should. : D

Basically, setting the field to NULL will simply save the NULL value. However, if I didn't choose an option (i.e. chose NULL) via a field widget on the edit form, no value would be saved at all. The problem then is that when I try to wrap the entity later, it's choking on this NULL value. What we really need is a way to remove a field's value from the database altogether as though we had "unselected" the option from the edit form.

The reason this is a problem is b/c when I come back and try to wrap the node after its product reference field value has been set to NULL, I get an array flip error resulting from the wrapper trying to do a commerce_product_load(NULL).

Summary: the patch does what it needs to do, but Entity ought to do more to actually resolve this issue.

w00t! That did the trick. : )