java.lang.NullPointerException: null
	at org.hibernate.event.internal.AbstractFlushingEventListener.prepareEntityFlushes(AbstractFlushingEventListener.java:147) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final]
	at org.hibernate.event.internal.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:83) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final]
	at org.hibernate.event.internal.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:38) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final]
	at org.hibernate.internal.SessionImpl.doFlush(SessionImpl.java:1454) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final]
	at org.hibernate.internal.SessionImpl.managedFlush(SessionImpl.java:511) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final]
	at org.hibernate.internal.SessionImpl.flushBeforeTransactionCompletion(SessionImpl.java:3290) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final]
	at org.hibernate.internal.SessionImpl.beforeTransactionCompletion(SessionImpl.java:2486) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final]
	at org.hibernate.engine.jdbc.internal.JdbcCoordinatorImpl.beforeTransactionCompletion(JdbcCoordinatorImpl.java:473) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final]
	at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl.beforeCompletionCallback(JdbcResourceLocalTransactionCoordinatorImpl.java:178) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final]
	at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl.access$300(JdbcResourceLocalTransactionCoordinatorImpl.java:39) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final]
	at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl$TransactionDriverControlImpl.commit(JdbcResourceLocalTransactionCoordinatorImpl.java:271) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final]
	at org.hibernate.engine.transaction.internal.TransactionImpl.commit(TransactionImpl.java:104) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final]
	at org.springframework.orm.jpa.JpaTransactionManager.doCommit(JpaTransactionManager.java:532) ~[spring-orm-5.1.7.RELEASE.jar:5.1.7.RELEASE]
	at org.springframework.transaction.support.AbstractPlatformTransactionManager.processCommit(AbstractPlatformTransactionManager.java:746) ~[spring-tx-5.1.7.RELEASE.jar:5.1.7.RELEASE]
	at org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:714) ~[spring-tx-5.1.7.RELEASE.jar:5.1.7.RELEASE]
	at org.springframework.transaction.interceptor.TransactionAspectSupport.commitTransactionAfterReturning(TransactionAspectSupport.java:534) ~[spring-tx-5.1.7.RELEASE.jar:5.1.7.RELEASE]
	at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:305) ~[spring-tx-5.1.7.RELEASE.jar:5.1.7.RELEASE]
	at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:98) ~[spring-tx-5.1.7.RELEASE.jar:5.1.7.RELEASE]
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.7.RELEASE.jar:5.1.7.RELEASE]
	at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:139) ~[spring-tx-5.1.7.RELEASE.jar:5.1.7.RELEASE]
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.7.RELEASE.jar:5.1.7.RELEASE]
	at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:138) ~[spring-data-jpa-2.1.8.RELEASE.jar:2.1.8.RELEASE]
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.7.RELEASE.jar:5.1.7.RELEASE]
	at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:93) ~[spring-aop-5.1.7.RELEASE.jar:5.1.7.RELEASE]
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.7.RELEASE.jar:5.1.7.RELEASE]
	at org.springframework.data.repository.core.support.SurroundingTransactionDetectorMethodInterceptor.invoke(SurroundingTransactionDetectorMethodInterceptor.java:61) ~[spring-data-commons-2.1.8.RELEASE.jar:2.1.8.RELEASE]
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.7.RELEASE.jar:5.1.7.RELEASE]
	at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212) ~[spring-aop-5.1.7.RELEASE.jar:5.1.7.RELEASE]
	at com.sun.proxy.$Proxy170.save(Unknown Source) ~[na:na]