Error when a product has SKU = null

[gonzaloebiz]

In magento2, the sku is required, but you can go to stores/products/attributes and search for sku and put it like not required

If you go to the product, you have no way to set the SKU as null, so you must edit directly the table catalog_product_entity and put a null in the corresponding row
Then try to modify the product (or simply save it), and you can view that is not possible, so you must mark it as modified directly in the mailchimp_sync_ecommerce table (search for type = 'PRO' and related_id = yourProductId)

This situation can't happens naturally in magento, but if you put the sku as not required and import products without sku or add products in some other programmatic way with no sku