java.lang.NullPointerException: Cannot invoke "org.hibernate.persister.collection.CollectionPersister.getRole()" because "this.loadedPersister" is null

@Getter
@Setter
@Entity
@Table(name = "CUSTOMER")
@SequenceGenerator(name = "SEQ_CUSTOMER_ID", allocationSize = 10, sequenceName = "SEQ_CUSTOMER_ID")
public class Customer {

    @Id
    @Column(name = "ID")
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "SEQ_CUSTOMER_ID")
    private Long id;

    @Column(name = "NAME")
    private String name;

    @OneToMany(mappedBy = "customer", cascade = CascadeType.ALL, orphanRemoval = true)
    private List<Sale> sales = new ArrayList<>();

}

@Getter
@Setter
@Entity
@Table(name = "SALE")
@SequenceGenerator(name = "SEQ_SALE_ID", allocationSize = 10, sequenceName = "SEQ_SALE_ID")
public class Sale {

    @Id
    @Column(name = "ID")
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "SEQ_SALE_ID")
    private Long id;

    @Column(name = "INDENTIFIER")
    private String indentifier;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "ID_CUSTOMER")
    private Customer customer;

    @OneToMany(mappedBy = "sale", cascade = CascadeType.ALL)
    private List<SaleLine> saleLines = new ArrayList<>();
}

@Data
@ToString(exclude = {"sale"})
@Entity
@Table(name = "SALELINE")
@SequenceGenerator(name = "SEQ_SALELINE_ID", allocationSize = 10, sequenceName = "SEQ_SALELINE_ID")
public class SaleLine {

    @Id
    @Column(name = "ID")
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "SEQ_SALELINE_ID")
    private Long id;

    @Column(name = "INDENTIFIER")
    private String identifier;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "ID_SALE", nullable = false)
    private Sale sale;
}

@Test
	public void add_customer_sale_ko_collection() {
		// first creating the customer
		Customer customer = new Customer();
		customer.setName("Customer Z");
		customer = customerRepository.save(customer);

		// then adding the sale
		Sale sale = new Sale();
		sale.setIndentifier("Customer Z sale");
		SaleLine saleLine = new SaleLine();
		saleLine.setIdentifier("some product sold");
		saleLine.setSale(sale);
		sale.getSaleLines().add(saleLine);

		customer.getSales().add(sale);
		sale.setCustomer(customer);
		customerRepository.save(customer);
	}