Getting ERROR "JBAS014612: Operation ("clean-obsolete-content") failed - address: ([]): java.lang.NullPointerException" in JBoss EAP 6

Issue

The following NullPointerException happens randomly in JBoss EAP 6:

ERROR [org.jboss.as.controller.management-operation] (ServerService Thread Pool -- 57) JBAS014612: Operation ("clean-obsolete-content") failed - address: ([]): java.lang.NullPointerException
    at org.jboss.as.repository.ContentRepository$Factory$ContentRepositoryImpl.listLocalContents(ContentRepository.java:442) [jboss-as-deployment-repository-7.5.10.Final-redhat-2.jar:7.5.10.Final-redhat-2]
    at org.jboss.as.repository.ContentRepository$Factory$ContentRepositoryImpl.cleanObsoleteContent(ContentRepository.java:404) [jboss-as-deployment-repository-7.5.10.Final-redhat-2.jar:7.5.10.Final-redhat-2]
    at org.jboss.as.server.operations.CleanObsoleteContentHandler.execute(CleanObsoleteContentHandler.java:75) [jboss-as-server-7.5.10.Final-redhat-2.jar:7.5.10.Final-redhat-2]
    at org.jboss.as.controller.AbstractOperationContext.executeStep(AbstractOperationContext.java:708) [jboss-as-controller-7.5.10.Final-redhat-2.jar:7.5.10.Final-redhat-2]
    at org.jboss.as.controller.AbstractOperationContext.doCompleteStep(AbstractOperationContext.java:543) [jboss-as-controller-7.5.10.Final-redhat-2.jar:7.5.10.Final-redhat-2]
    at org.jboss.as.controller.AbstractOperationContext.completeStepInternal(AbstractOperationContext.java:338) [jboss-as-controller-7.5.10.Final-redhat-2.jar:7.5.10.Final-redhat-2]
    at org.jboss.as.controller.AbstractOperationContext.executeOperation(AbstractOperationContext.java:314) [jboss-as-controller-7.5.10.Final-redhat-2.jar:7.5.10.Final-redhat-2]
    at org.jboss.as.controller.OperationContextImpl.executeOperation(OperationContextImpl.java:1144) [jboss-as-controller-7.5.10.Final-redhat-2.jar:7.5.10.Final-redhat-2]
    at org.jboss.as.controller.ModelControllerImpl.internalExecute(ModelControllerImpl.java:331) [jboss-as-controller-7.5.10.Final-redhat-2.jar:7.5.10.Final-redhat-2]
    at org.jboss.as.controller.ModelControllerImpl.execute(ModelControllerImpl.java:188) [jboss-as-controller-7.5.10.Final-redhat-2.jar:7.5.10.Final-redhat-2]
    at org.jboss.as.controller.ModelControllerImpl$3.execute(ModelControllerImpl.java:563) [jboss-as-controller-7.5.10.Final-redhat-2.jar:7.5.10.Final-redhat-2]
    at org.jboss.as.controller.ModelControllerImpl$3.execute(ModelControllerImpl.java:553) [jboss-as-controller-7.5.10.Final-redhat-2.jar:7.5.10.Final-redhat-2]
    at org.jboss.as.server.deployment.ContentRepositoryCleaner.cleanObsoleteContent(ContentRepositoryCleaner.java:132) [jboss-as-server-7.5.10.Final-redhat-2.jar:7.5.10.Final-redhat-2]
    at org.jboss.as.server.deployment.ContentRepositoryCleaner$ContentRepositoryCleanerTask.run(ContentRepositoryCleaner.java:67) [jboss-as-server-7.5.10.Final-redhat-2.jar:7.5.10.Final-redhat-2]
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [rt.jar:1.8.0_101]
    at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308) [rt.jar:1.8.0_101]
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180) [rt.jar:1.8.0_101]
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294) [rt.jar:1.8.0_101]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [rt.jar:1.8.0_101]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [rt.jar:1.8.0_101]
    at java.lang.Thread.run(Thread.java:745) [rt.jar:1.8.0_101]
    at org.jboss.threads.JBossThread.run(JBossThread.java:122) [jboss-threads-2.1.2.Final-redhat-1.jar:2.1.2.Final-redhat-1]