When updating or adding a value, it gives an error regarding the VariantID even though it’s defined as nullable.

model CartItem {
  id        Int      @id @default(autoincrement())
  quantity  Int      @default(1)
  cart      Cart     @relation(fields: [cartId], references: [id])
  cartId    Int
  variant   Variant? @relation(fields: [variantId], references: [id])
  variantId Int?
  product   Product  @relation(fields: [productId], references: [id])
  productId Int
  @@unique([cartId, productId, variantId])
}

error is

Invalid `prisma.cartItem.findUnique()` invocation:

{
  where: {
    cartId_productId_variantId: {
      cartId: 1,
      productId: 6,
+     variantId: Int
    }
  }
}

Argument `variantId` must not be null.