JBoss throws JBAS012656 Default JSF implementation slot XXX is invalid ERROR in EAP 6 ?

Issue

• Why JBoss is throwing the following JBAS012656: Default JSF implementation slot 'abc' is invalid ERROR while starting the JBoss:

11:13:12,357 WARN  [org.jboss.as.jsf] (MSC service thread 1-4) JBAS012603: Unknown JSF version 'Mojarra-2.0'.  Default version 'abc' will be used instead.
11:13:12,360 ERROR [org.jboss.msc.service.fail] (MSC service thread 1-4) MSC000001: Failed to start service jboss.deployment.subunit."A.ear"."B.war".DEPENDENCIES: org.jboss.msc.service.StartException in service jboss.deployment.subunit."A.ear"."B.war".DEPENDENCIES: JBAS018733: Failed to process phase DEPENDENCIES of subdeployment "B.war" of deployment "A.ear"
    at org.jboss.as.server.deployment.DeploymentUnitPhaseService.start(DeploymentUnitPhaseService.java:127) [jboss-as-server-7.3.0.Final-redhat-14.jar:7.3.0.Final-redhat-14]
    at org.jboss.msc.service.ServiceControllerImpl$StartTask.startService(ServiceControllerImpl.java:1811) [jboss-msc-1.0.4.GA-redhat-1.jar:1.0.4.GA-redhat-1]
    at org.jboss.msc.service.ServiceControllerImpl$StartTask.run(ServiceControllerImpl.java:1746) [jboss-msc-1.0.4.GA-redhat-1.jar:1.0.4.GA-redhat-1]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) [rt.jar:1.7.0_17]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) [rt.jar:1.7.0_17]
    at java.lang.Thread.run(Thread.java:722) [rt.jar:1.7.0_17]
Caused by: org.jboss.as.server.deployment.DeploymentUnitProcessingException: JBAS012656: Default JSF implementation slot 'abc' is invalid
    at org.jboss.as.jsf.deployment.JSFDependencyProcessor.deploy(JSFDependencyProcessor.java:78)
    at org.jboss.as.server.deployment.DeploymentUnitPhaseService.start(DeploymentUnitPhaseService.java:120) [jboss-as-server-7.3.0.Final-redhat-14.jar:7.3.0.Final-redhat-14]
    ... 5 more