How do I avoid the ERROR message "KC-SERVICES0089: Failed to run scheduled task ClearExpiredUserSessions"?

Issue

• The following error is logged repeatedly

WARN  [org.hibernate.engine.jdbc.spi.SqlExceptionHelper] (Timer-2) SQL Error: 0, SQLState: 08003
ERROR [org.hibernate.engine.jdbc.spi.SqlExceptionHelper] (Timer-2) This connection has been closed.
ERROR [org.keycloak.services] (Timer-2) KC-SERVICES0089: Failed to run scheduled task ClearExpiredUserSessions: javax.persistence.PersistenceException: org.hibernate.exception.JDBCConnectionException: could not prepare statement
 at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1692)
 at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1602)
 at org.hibernate.jpa.internal.QueryImpl.getResultList(QueryImpl.java:492)
 at org.keycloak.models.jpa.JpaRealmProvider.getRealms(JpaRealmProvider.java:99)
 at org.keycloak.models.cache.infinispan.RealmCacheSession.getRealms(RealmCacheSession.java:447)
 at org.keycloak.services.scheduled.ClearExpiredUserSessions.run(ClearExpiredUserSessions.java:35)
 at org.keycloak.services.scheduled.ScheduledTaskRunner.runTask(ScheduledTaskRunner.java:61)
 at org.keycloak.services.scheduled.ScheduledTaskRunner.run(ScheduledTaskRunner.java:45)
 at org.keycloak.timer.basic.BasicTimerProvider$1.run(BasicTimerProvider.java:51)
 at java.util.TimerThread.mainLoop(Timer.java:555)
 at java.util.TimerThread.run(Timer.java:505)
 Caused by: org.hibernate.exception.JDBCConnectionException: could not prepare statement
 at org.hibernate.exception.internal.SQLStateConversionDelegate.convert(SQLStateConversionDelegate.java:115)
 at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:42)
 at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:111)
 at org.hibernate.engine.jdbc.internal.StatementPreparerImpl$StatementPreparationTemplate.prepareStatement(StatementPreparerImpl.java:182)
 at org.hibernate.engine.jdbc.internal.StatementPreparerImpl.prepareQueryStatement(StatementPreparerImpl.java:148)
 at org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1934)
 at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1903)
 at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1881)
 at org.hibernate.loader.Loader.doQuery(Loader.java:925)
 at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:342)
 at org.hibernate.loader.Loader.doList(Loader.java:2622)
 at org.hibernate.loader.Loader.doList(Loader.java:2605)
 at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2434)
 at org.hibernate.loader.Loader.list(Loader.java:2429)
 at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:501)
 at org.hibernate.hql.internal.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:371)
 at org.hibernate.engine.query.spi.HQLQueryPlan.performList(HQLQueryPlan.java:216)
 at org.hibernate.internal.SessionImpl.list(SessionImpl.java:1339)
 at org.hibernate.internal.QueryImpl.list(QueryImpl.java:87)
 at org.hibernate.jpa.internal.QueryImpl.list(QueryImpl.java:606)
 at org.hibernate.jpa.internal.QueryImpl.getResultList(QueryImpl.java:483)
 ... 8 more
 Caused by: org.postgresql.util.PSQLException: This connection has been closed.
 at org.postgresql.jdbc2.AbstractJdbc2Connection.checkClosed(AbstractJdbc2Connection.java:822)
 at org.postgresql.jdbc3.AbstractJdbc3Connection.prepareStatement(AbstractJdbc3Connection.java:273)
 at org.jboss.jca.adapters.jdbc.BaseWrapperManagedConnection.doPrepareStatement(BaseWrapperManagedConnection.java:757)
 at org.jboss.jca.adapters.jdbc.BaseWrapperManagedConnection.prepareStatement(BaseWrapperManagedConnection.java:743)
 at org.jboss.jca.adapters.jdbc.WrappedConnection.prepareStatement(WrappedConnection.java:454)
 at org.hibernate.engine.jdbc.internal.StatementPreparerImpl$5.doPrepare(StatementPreparerImpl.java:146)
 at org.hibernate.engine.jdbc.internal.StatementPreparerImpl$StatementPreparationTemplate.prepareStatement(StatementPreparerImpl.java:172)
 ... 25 more