AssertionFailure in XWiki 0.9.794

I'm using Tomcat 5.9 with XWiki 0.9.794. When i login to xwiki it throws an error like this, 18:14:40,479 ERROR http-8081-Processor23 http://localhost:8878/xwiki/bin/view/Ma in/WebHome AssertionFailure:<init>:22 - an assertion failure occured (this may i ndicate a bug in Hibernate, but is more likely due to unsafe use of the session) org.hibernate.AssertionFailure: possible nonthreadsafe access to session at org.hibernate.action.EntityDeleteAction.execute(EntityDeleteAction.ja va:68) at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:239) at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:223) at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:141) at org.hibernate.event.def.AbstractFlushingEventListener.performExecutio ns(AbstractFlushingEventListener.java:274) at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlus hEventListener.java:27) at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:726) at org.hibernate.impl.SessionImpl.managedFlush(SessionImpl.java:320) at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java :86) at com.xpn.xwiki.store.XWikiHibernateStore.endTransaction(XWikiHibernate Store.java:342) at com.xpn.xwiki.store.XWikiHibernateStore.deleteXWikiCollection(XWikiHi bernateStore.java:974) at com.xpn.xwiki.stats.impl.XWikiStatsServiceImpl.notify(XWikiStatsServi ceImpl.java:205) at com.xpn.xwiki.notify.XWikiActionRule.verify(XWikiActionRule.java:51) at com.xpn.xwiki.notify.XWikiNotificationManager.verify(XWikiNotificatio nManager.java:93) at com.srilogic.xwiki.user.web.ViewEditAction.execute(ViewEditAction.jav a:283) at org.apache.struts.action.RequestProcessor.processActionPerform(Reques tProcessor.java:421) at org.apache.struts.action.RequestProcessor.process(RequestProcessor.ja va:226) at org.apache.struts.action.ActionServlet.process(ActionServlet.java:116 4) at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:397) at javax.servlet.http.HttpServlet.service(HttpServlet.java:689) at javax.servlet.http.HttpServlet.service(HttpServlet.java:802) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(Appl icationFilterChain.java:252) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationF ilterChain.java:173) at com.xpn.xwiki.web.SetCharacterEncodingFilter.doFilter(SetCharacterEnc odingFilter.java:127) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(Appl icationFilterChain.java:202) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationF ilterChain.java:173) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperV alve.java:213) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextV alve.java:178) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.j ava:126) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.j ava:105) at com.srilogic.iportal.security.catalina.authenticator.SingleSignOn.inv oke(SingleSignOn.java:374) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineVal ve.java:107) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.jav a:148) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java :856) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.proce ssConnection(Http11Protocol.java:744) at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpo int.java:527) at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFol lowerWorkerThread.java:80) at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadP ool.java:684) at java.lang.Thread.run(Thread.java:534) com.xpn.xwiki.XWikiException: Error number 3213 in 3: Exception while deleting o bject XWiki.admin Wrapped Exception: possible nonthreadsafe access to session at com.xpn.xwiki.store.XWikiHibernateStore.deleteXWikiCollection(XWikiHi bernateStore.java:978) at com.xpn.xwiki.stats.impl.XWikiStatsServiceImpl.notify(XWikiStatsServi ceImpl.java:205) at com.xpn.xwiki.notify.XWikiActionRule.verify(XWikiActionRule.java:51) at com.xpn.xwiki.notify.XWikiNotificationManager.verify(XWikiNotificatio nManager.java:93) at com.srilogic.xwiki.user.web.ViewEditAction.execute(ViewEditAction.jav a:283) at org.apache.struts.action.RequestProcessor.processActionPerform(Reques tProcessor.java:421) at org.apache.struts.action.RequestProcessor.process(RequestProcessor.ja va:226) at org.apache.struts.action.ActionServlet.process(ActionServlet.java:116 4) at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:397) at javax.servlet.http.HttpServlet.service(HttpServlet.java:689) at javax.servlet.http.HttpServlet.service(HttpServlet.java:802) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(Appl icationFilterChain.java:252) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationF ilterChain.java:173) at com.xpn.xwiki.web.SetCharacterEncodingFilter.doFilter(SetCharacterEnc odingFilter.java:127) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(Appl icationFilterChain.java:202) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationF ilterChain.java:173) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperV alve.java:213) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextV alve.java:178) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.j ava:126) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.j ava:105) at com.srilogic.iportal.security.catalina.authenticator.SingleSignOn.inv oke(SingleSignOn.java:374) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineVal ve.java:107) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.jav a:148) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java :856) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.proce ssConnection(Http11Protocol.java:744) at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpo int.java:527) at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFol lowerWorkerThread.java:80) at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadP ool.java:684) at java.lang.Thread.run(Thread.java:534) Wrapped Exception: org.hibernate.AssertionFailure: possible nonthreadsafe access to session at org.hibernate.action.EntityDeleteAction.execute(EntityDeleteAction.ja va:68) at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:239) at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:223) at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:141) at org.hibernate.event.def.AbstractFlushingEventListener.performExecutio ns(AbstractFlushingEventListener.java:274) at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlus hEventListener.java:27) at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:726) at org.hibernate.impl.SessionImpl.managedFlush(SessionImpl.java:320) at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java :86) at com.xpn.xwiki.store.XWikiHibernateStore.endTransaction(XWikiHibernate Store.java:342) at com.xpn.xwiki.store.XWikiHibernateStore.deleteXWikiCollection(XWikiHi bernateStore.java:974) at com.xpn.xwiki.stats.impl.XWikiStatsServiceImpl.notify(XWikiStatsServi ceImpl.java:205) at com.xpn.xwiki.notify.XWikiActionRule.verify(XWikiActionRule.java:51) at com.xpn.xwiki.notify.XWikiNotificationManager.verify(XWikiNotificatio nManager.java:93) at com.srilogic.xwiki.user.web.ViewEditAction.execute(ViewEditAction.jav a:283) at org.apache.struts.action.RequestProcessor.processActionPerform(Reques tProcessor.java:421) at org.apache.struts.action.RequestProcessor.process(RequestProcessor.ja va:226) at org.apache.struts.action.ActionServlet.process(ActionServlet.java:116 4) at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:397) at javax.servlet.http.HttpServlet.service(HttpServlet.java:689) at javax.servlet.http.HttpServlet.service(HttpServlet.java:802) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(Appl icationFilterChain.java:252) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationF ilterChain.java:173) at com.xpn.xwiki.web.SetCharacterEncodingFilter.doFilter(SetCharacterEnc odingFilter.java:127) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(Appl icationFilterChain.java:202) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationF ilterChain.java:173) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperV alve.java:213) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextV alve.java:178) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.j ava:126) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.j ava:105) at com.srilogic.iportal.security.catalina.authenticator.SingleSignOn.inv oke(SingleSignOn.java:374) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineVal ve.java:107) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.jav a:148) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java :856) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.proce ssConnection(Http11Protocol.java:744) at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpo int.java:527) at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFol lowerWorkerThread.java:80) at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadP ool.java:684) at java.lang.Thread.run(Thread.java:534) 18:14:43,133 WARN http-8081-Processor24 RequestUtils:createActionForm:177 - No FormBeanConfig found under 'skin' Finally it says No FormBeanConfig found under 'skin'. If i'm correct something is missing in the struts-config.xml. But i'm not sure whether this is relevant to above exception