potential NPE in ReplicaSetInfo

java.lang.NullPointerException: null
        at com.google.common.base.Preconditions.checkNotNull(Preconditions.java:192) ~[oak-run-1.8-SNAPSHOT.jar:1.8-SNAPSHOT]
        at com.google.common.collect.SingletonImmutableSet.<init>(SingletonImmutableSet.java:47) ~[oak-run-1.8-SNAPSHOT.jar:1.8-SNAPSHOT]
        at com.google.common.collect.ImmutableSet.of(ImmutableSet.java:94) ~[oak-run-1.8-SNAPSHOT.jar:1.8-SNAPSHOT]
        at org.apache.jackrabbit.oak.plugins.document.mongo.replica.ReplicaSetInfo.updateRevisions(ReplicaSetInfo.java:264) ~[oak-run-1.8-SNAPSHOT.jar:1.8-SNAPSHOT]
        at org.apache.jackrabbit.oak.plugins.document.mongo.replica.ReplicaSetInfo.updateReplicaStatus(ReplicaSetInfo.java:182) ~[oak-run-1.8-SNAPSHOT.jar:1.8-SNAPSHOT]
        at org.apache.jackrabbit.oak.plugins.document.mongo.replica.ReplicaSetInfo.updateLoop(ReplicaSetInfo.java:145) ~[oak-run-1.8-SNAPSHOT.jar:1.8-SNAPSHOT]
        at org.apache.jackrabbit.oak.plugins.document.mongo.replica.ReplicaSetInfo.run(ReplicaSetInfo.java:134) ~[oak-run-1.8-SNAPSHOT.jar:1.8-SNAPSHOT]
        at java.lang.Thread.run(Unknown Source) [na:1.8.0_121]