Error logged when attempting to passivate invalidated session

Handle this more cleanly:

[JBoss] 12:52:31,124 ERROR [JBossCacheManager] processExpirationPassivation(): failed passivating session Xb2xu1VGptWjgAU3adPjTw__
[JBoss] java.lang.IllegalStateException: getLastAccessedTime: Session already invalidated
[JBoss] at org.jboss.web.tomcat.service.session.ClusteredSession.getLastAccessedTime(ClusteredSession.java:498)
[JBoss] at org.jboss.web.tomcat.service.session.JBossCacheManager.processSessionPassivation(JBossCacheManager.java:1665)
[JBoss] at org.jboss.web.tomcat.service.session.JBossCacheManager.access$600(JBossCacheManager.java:71)
[JBoss] at org.jboss.web.tomcat.service.session.JBossCacheManager$PassivationCheck.passivate(JBossCacheManager.java:2288)
[JBoss] at org.jboss.web.tomcat.service.session.JBossCacheManager$PassivationCheck.access$300(JBossCacheManager.java:2254)
[JBoss] at org.jboss.web.tomcat.service.session.JBossCacheManager.processExpirationPassivation(JBossCacheManager.java:1308)
[JBoss] at org.jboss.web.tomcat.service.session.JBossManager.backgroundProcess(JBossManager.java:353)
[JBoss] at org.apache.catalina.core.ContainerBase.backgroundProcess(ContainerBase.java:1327)
[JBoss] at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1612)
[JBoss] at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1621)
[JBoss] at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1621)
[JBoss] at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1601)
[JBoss] at java.lang.Thread.run(Thread.java:619)