EAP 7 throws NullPointerException in distributable session invalidation

Issue

• We see the following NullPointerException in session invalidation:

java.lang.NullPointerException
        at org.wildfly.clustering.ee.cache@7.3.6.GA-redhat-00002//org.wildfly.clustering.ee.cache.ConcurrentManager$2.apply(ConcurrentManager.java:60)
        at org.wildfly.clustering.ee.cache@7.3.6.GA-redhat-00002//org.wildfly.clustering.ee.cache.ConcurrentManager$2.apply(ConcurrentManager.java:57)
        at java.base/java.util.concurrent.ConcurrentHashMap.compute(ConcurrentHashMap.java:1908)
        at org.wildfly.clustering.ee.cache@7.3.6.GA-redhat-00002//org.wildfly.clustering.ee.cache.ConcurrentManager$3.run(ConcurrentManager.java:87)
        at org.wildfly.clustering.web.cache@7.3.6.GA-redhat-00002//org.wildfly.clustering.web.cache.session.ConcurrentSessionManager$ConcurrentSession.invalidate(ConcurrentSessionManager.java:177)
        at org.wildfly.clustering.web.undertow@7.3.6.GA-redhat-00002//org.wildfly.clustering.web.undertow.session.DistributableSession.invalidate(DistributableSession.java:236)
        at io.undertow.servlet@2.0.34.SP1-redhat-00001//io.undertow.servlet.spec.HttpSessionImpl.invalidate(HttpSessionImpl.java:198)