我是新的Spring和学习JPA实体关系，我有两个实体定义在我的项目有双向多到多Map，请避免任何错误，如果我犯了，并帮助我解决这个问题。
Account.java

@NoArgsConstructor
@AllArgsConstructor
@Data
@Builder
@Entity
@Table(name = "account")
public class Account {

    @Id
    private int id;

    private String password;

    @ManyToMany(cascade = CascadeType.ALL, mappedBy = "accounts")
    private List<Employee> employees;

}

Employee.java

@NoArgsConstructor
@AllArgsConstructor
@Data
@Builder
@Entity
@Table(name = "employee")
public class Employee {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;

    private String name;
    private String email;

    @ManyToMany(mappedBy = "employee" )
    private List<Account> accounts;

}

但是当运行服务器时我得到这个错误

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaConfiguration.class]: Cannot invoke "org.hibernate.mapping.ToOne.getReferencedEntityName()" because "toOne" is null
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1770) ~[spring-beans-6.0.11.jar:6.0.11]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:598) ~[spring-beans-6.0.11.jar:6.0.11]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:520) ~[spring-beans-6.0.11.jar:6.0.11]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:326) ~[spring-beans-6.0.11.jar:6.0.11]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234) ~[spring-beans-6.0.11.jar:6.0.11]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:324) ~[spring-beans-6.0.11.jar:6.0.11]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:200) ~[spring-beans-6.0.11.jar:6.0.11]
    at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1155) ~[spring-context-6.0.11.jar:6.0.11]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:932) ~[spring-context-6.0.11.jar:6.0.11]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:608) ~[spring-context-6.0.11.jar:6.0.11]
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:146) ~[spring-boot-3.1.2.jar:3.1.2]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:734) ~[spring-boot-3.1.2.jar:3.1.2]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:436) ~[spring-boot-3.1.2.jar:3.1.2]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:312) ~[spring-boot-3.1.2.jar:3.1.2]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1306) ~[spring-boot-3.1.2.jar:3.1.2]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1295) ~[spring-boot-3.1.2.jar:3.1.2]
    at com.example.examDummy.ExamDummyApplication.main(ExamDummyApplication.java:10) ~[classes/:na]
Caused by: java.lang.NullPointerException: Cannot invoke "org.hibernate.mapping.ToOne.getReferencedEntityName()" because "toOne" is null
    at org.hibernate.boot.model.internal.BinderHelper.checkMappedByType(BinderHelper.java:1088) ~[hibernate-core-6.2.6.Final.jar:6.2.6.Final]
    at org.hibernate.boot.model.internal.CollectionBinder.isReversePropertyInJoin(CollectionBinder.java:1571) ~[hibernate-core-6.2.6.Final.jar:6.2.6.Final]
    at org.hibernate.boot.model.internal.CollectionBinder.noAssociationTable(CollectionBinder.java:1582) ~[hibernate-core-6.2.6.Final.jar:6.2.6.Final]
    at org.hibernate.boot.model.internal.CollectionBinder.bindStarToManySecondPass(CollectionBinder.java:1543) ~[hibernate-core-6.2.6.Final.jar:6.2.6.Final]
    at org.hibernate.boot.model.internal.CollectionBinder$1.secondPass(CollectionBinder.java:1534) ~[hibernate-core-6.2.6.Final.jar:6.2.6.Final]
    at org.hibernate.boot.model.internal.CollectionSecondPass.doSecondPass(CollectionSecondPass.java:45) ~[hibernate-core-6.2.6.Final.jar:6.2.6.Final]
    at org.hibernate.boot.internal.InFlightMetadataCollectorImpl.processSecondPasses(InFlightMetadataCollectorImpl.java:1857) ~[hibernate-core-6.2.6.Final.jar:6.2.6.Final]
    at org.hibernate.boot.internal.InFlightMetadataCollectorImpl.processSecondPasses(InFlightMetadataCollectorImpl.java:1814) ~[hibernate-core-6.2.6.Final.jar:6.2.6.Final]
    at org.hibernate.boot.model.process.spi.MetadataBuildingProcess.complete(MetadataBuildingProcess.java:328) ~[hibernate-core-6.2.6.Final.jar:6.2.6.Final]
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.metadata(EntityManagerFactoryBuilderImpl.java:1380) ~[hibernate-core-6.2.6.Final.jar:6.2.6.Final]
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:1451) ~[hibernate-core-6.2.6.Final.jar:6.2.6.Final]
    at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:75) ~[spring-orm-6.0.11.jar:6.0.11]
    at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:376) ~[spring-orm-6.0.11.jar:6.0.11]
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory(AbstractEntityManagerFactoryBean.java:409) ~[spring-orm-6.0.11.jar:6.0.11]
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:396) ~[spring-orm-6.0.11.jar:6.0.11]
    at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.afterPropertiesSet(LocalContainerEntityManagerFactoryBean.java:352) ~[spring-orm-6.0.11.jar:6.0.11]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1817) ~[spring-beans-6.0.11.jar:6.0.11]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1766) ~[spring-beans-6.0.11.jar:6.0.11]
    ... 16 common frames omitted

Process finished with exit code 1

请帮助我了解此错误以及发生的原因。