Undefined error while saving product if additional part left blank

1. Create or edit a product.

2. Change the category to Avatar Addon.

3. Flip the switch to enable additional unique assets.

4. Click the button for "My product has another asset"

5. Flip the switch back off without removing that entry.

6. Attempt to save.

"Undefined" will display below the category picker and asset details will fail to save.