Add even when object is null?

export const userItems = pgTable("userItem", {
        product_id: serial("product_id").notNull(),
        user_id: text("user_id").notNull(),
        quantity: integer("quantity")
    },
    (userItems) => ({
            compoundKey: primaryKey(userItems.product_id, userItems.user_id),
        }
    )
)

export const userItemsRelations = relations(userItems, ({one}) => ({
    product: one(products, {
        fields: [userItems.product_id],
        references: [products.id]
    }),

    user: one(users, {
        fields: [userItems.user_id],
        references: [users.id]
    }),
}))