14:49:55,859 ERROR [org.modeshape.jcr.JcrRepository] (modeshape-gc-6-thread-1) Error during background garbage collection: null: java.lang.NullPointerException
        at org.modeshape.jcr.SystemContent.first(SystemContent.java:647) [modeshape-jcr-3.7.1.Final.jar:3.7.1.Final]
        at org.modeshape.jcr.SystemContent.first(SystemContent.java:641) [modeshape-jcr-3.7.1.Final.jar:3.7.1.Final]
        at org.modeshape.jcr.SystemContent.cleanUpLocks(SystemContent.java:818) [modeshape-jcr-3.7.1.Final.jar:3.7.1.Final]
        at org.modeshape.jcr.JcrRepository$RunningState.cleanUpLocks(JcrRepository.java:1790) [modeshape-jcr-3.7.1.Final.jar:3.7.1.Final]
        at org.modeshape.jcr.JcrRepository$LockGarbageCollectionTask.doRun(JcrRepository.java:2125) [modeshape-jcr-3.7.1.Final.jar:3.7.1.Final]
        at org.modeshape.jcr.JcrRepository$BackgroundRepositoryTask.run(JcrRepository.java:2095) [modeshape-jcr-3.7.1.Final.jar:3.7.1.Final]
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441) [rt.jar:1.6.0_27]
        at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:317) [rt.jar:1.6.0_27]
        at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:150) [rt.jar:1.6.0_27]
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$101(ScheduledThreadPoolExecutor.java:98) [rt.jar:1.6.0_27]
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.runPeriodic(ScheduledThreadPoolExecutor.java:180) [rt.jar:1.6.0_27]
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:204) [rt.jar:1.6.0_27]
        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) [rt.jar:1.6.0_27]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) [rt.jar:1.6.0_27]
        at java.lang.Thread.run(Thread.java:662) [rt.jar:1.6.0_27]