NullPointerException in SessionManagerStatsHandler.executeRuntimeStep

Issue

• We see the following NPE when checking web app attributes:

ERROR [org.jboss.as.controller.management-operation] (HttpManagementService-threads - 14) JBAS014612: Operation ("read-attribute") failed - address: ([
    {"deployment" => "app.war"},
    {"subsystem" => "web"}
]): java.lang.NullPointerException
        at org.jboss.as.web.WebDeploymentDefinition$SessionManagerStatsHandler.executeRuntimeStep(WebDeploymentDefinition.java:106)
        at org.jboss.as.controller.AbstractRuntimeOnlyHandler$1.execute(AbstractRuntimeOnlyHandler.java:90) [jboss-as-controller-7.1.3.Final-redhat-4.jar:7.1.3.Final-redhat-4]
        at org.jboss.as.controller.AbstractOperationContext.executeStep(AbstractOperationContext.java:397) [jboss-as-controller-7.1.3.Final-redhat-4.jar:7.1.3.Final-redhat-4]
        at org.jboss.as.controller.AbstractOperationContext.doCompleteStep(AbstractOperationContext.java:284) [jboss-as-controller-7.1.3.Final-redhat-4.jar:7.1.3.Final-redhat-4]
        at org.jboss.as.controller.AbstractOperationContext.completeStep(AbstractOperationContext.java:211) [jboss-as-controller-7.1.3.Final-redhat-4.jar:7.1.3.Final-redhat-4]
        at org.jboss.as.controller.ModelControllerImpl$DefaultPrepareStepHandler.execute(ModelControllerImpl.java:473) [jboss-as-controller-7.1.3.Final-redhat-4.jar:7.1.3.Final-redhat-4]
        at org.jboss.as.controller.AbstractOperationContext.executeStep(AbstractOperationContext.java:397) [jboss-as-controller-7.1.3.Final-redhat-4.jar:7.1.3.Final-redhat-4]
        at org.jboss.as.controller.AbstractOperationContext.doCompleteStep(AbstractOperationContext.java:284) [jboss-as-controller-7.1.3.Final-redhat-4.jar:7.1.3.Final-redhat-4]