Preconditions:

• Added attribute group
• Added 2 attributes e.g integer and color
• Added product type based on attribute group with selected toggle that fields are required (step1 of preconditions)
• Added product based on product type (step3 preconditions)

Steps to reproduce:

1. Log in to back office.
2. Go to Product catalog / Products.
3. Switch to 'Variants' tab.
4. Click on 'Add' button.
5. Fill in 'Code' input.
6. Fill in 'Integer' input.
7. Select a Color.
8. Click on 'Create' button.

Actual result:

See attached screenshot

JS exception occurs when on generate variants form.

Uncaught TypeError: Cannot read properties of null (reading 'value')
    at validateField (ibexa-product-catalog-edit-js.js:32:36)
    at Array.map (<anonymous>)
    at HTMLButtonElement.validateForm (ibexa-product-catalog-edit-js.js:38:60)
    at HTMLButtonElement.trigger (ibexa-admin-ui-layout-js.js:62810:28) 

Expected result:

No exception occurs.