I'm stuck on a problem related to ORM PRISMA.
My SCHEMA is

model customers {
  id          String      @id @default(uuid())
  name        String
  email       String?     @unique
  phone       String?     @unique
  notes       String?
  personType  PersonType?
  document    String?     @unique
  createdById String
  updatedById String
  createdAt   DateTime    @default(now())
  updatedAt   DateTime    @updatedAt
  deletedAt   DateTime?

  createdBy users   @relation("CustomerCreatedBy", fields: [createdById], references: [id])
  updatedBy users   @relation("CustomerUpdatedBy", fields: [updatedById], references: [id])
  sales     sales[]

  @@index([name])
}

model sales {
  id            String        @id @default(uuid())
  saleNumber    Int           @default(autoincrement())
  saleCode      String?       @unique
  customerId    String?
  subtotalValue Float
  discountValue Float
  totalValue    Float
  paymentMethod PaymentMethod
  notes         String?
  createdById   String
  updatedById   String
  createdAt     DateTime      @default(now())
  updatedAt     DateTime      @updatedAt
  deletedAt     DateTime?

  customer  customers?  @relation(fields: [customerId], references: [id])
  createdBy users       @relation("SaleCreatedBy", fields: [createdById], references: [id])
  updatedBy users       @relation("SaleUpdatedBy", fields: [updatedById], references: [id])
  items     saleItems[]

  @@index([createdById])
}

But when i make

let sale
  await prisma.$transaction(async tx => {
    sale = await tx.sales.create({
      data: {
        customer: saleData.customerId
          ? { connect: { id: saleData.customerId } }
          : undefined,
        subtotalValue: saleData.subtotalValue,
        discountValue: saleData.discountValue,
        totalValue: saleData.totalValue,
        paymentMethod: saleData.paymentMethod,
        notes: saleData.notes,
        createdBy: { connect: { id: userId } },
        updatedBy: { connect: { id: userId } },
      },
    })

I receive the error

PrismaClientValidationError: 
Invalid `prisma.sales.create()` invocation:

{
  data: {
    subtotalValue: 48.36,
    discountValue: 0,
    totalValue: 48.36,
    paymentMethod: "CASH",
    notes: "string",
    createdBy: {
      connect: {
        id: "5ad3693d-a786-4f31-8779-1da2cfb39ac9"
      }
    },
    updatedBy: {
      connect: {
        id: "5ad3693d-a786-4f31-8779-1da2cfb39ac9"
      }
    },
+   customer: {
+     create: customersCreateWithoutSalesInput | customersUncheckedCreateWithoutSalesInput,
+     connectOrCreate: customersCreateOrConnectWithoutSalesInput,
+     connect: customersWhereUniqueInput
+   }
  }
}

Argument `customer` is missing.

Therefore, if I send the customer as undefined, I get an error saying that the argument is missing; if I send the customer as null, I get the error "Argument `customer` must not be null." And so I don't know how I can create a sale without an associated customer.