Updating a matched link src/dest to non-existing node does not remove it from overlay topology

The underlaying link does get updated properly, however the overlaying topology stays intact, with the old link info.

The attempt to remove the link from overlay topology produces this exception:

2016-06-07 19:33:44,005 | ERROR | n-dispatcher-174 | DataTreeChangeListenerActor | 171 - org.opendaylight.controller.sal-distributed-datastore - 1.4.0.SNAPSHOT | Error notifying listener org.opendaylight.topoprocessing.nt.listener.NTUnderlayTopologyListener@167b2464
java.lang.NullPointerException: Tree must not be null
at com.google.common.base.Preconditions.checkNotNull(Preconditions.java:226)[52:com.google.guava:18.0.0]
at org.opendaylight.yangtools.yang.data.api.schema.NormalizedNodes.findNode(NormalizedNodes.java:77)[93:org.opendaylight.yangtools.yang-data-api:1.0.0.SNAPSHOT]
at org.opendaylight.topoprocessing.nt.translator.NTLinkTranslator.translate(NTLinkTranslator.java:87)[285:org.opendaylight.topoprocessing.nt:0.2.0.SNAPSHOT]
at org.opendaylight.topoprocessing.impl.translator.OverlayItemTranslator.translate(OverlayItemTranslator.java:47)[176:org.opendaylight.topoprocessing.impl:0.2.0.SNAPSHOT]
at org.opendaylight.topoprocessing.impl.writer.TopologyWriter.writeItem(TopologyWriter.java:155)[176:org.opendaylight.topoprocessing.impl:0.2.0.SNAPSHOT]
at org.opendaylight.topoprocessing.impl.operator.TopologyManager.removeOverlayItem(TopologyManager.java:147)[176:org.opendaylight.topoprocessing.impl:0.2.0.SNAPSHOT]
at org.opendaylight.topoprocessing.impl.operator.LinkCalculator.removeMatchedLink(LinkCalculator.java:207)[176:org.opendaylight.topoprocessing.impl:0.2.0.SNAPSHOT]
at org.opendaylight.topoprocessing.impl.operator.LinkCalculator.processUpdatedChanges(LinkCalculator.java:109)[176:org.opendaylight.topoprocessing.impl:0.2.0.SNAPSHOT]
at org.opendaylight.topoprocessing.impl.listener.UnderlayTopologyListener.proceedChangeRequest(UnderlayTopologyListener.java:149)[176:org.opendaylight.topoprocessing.impl:0.2.0.SNAPSHOT]
at org.opendaylight.topoprocessing.impl.listener.UnderlayTopologyListener.onDataTreeChanged(UnderlayTopologyListener.java:85)[176:org.opendaylight.topoprocessing.impl:0.2.0.SNAPSHOT]
at org.opendaylight.controller.cluster.datastore.DataTreeChangeListenerActor.dataChanged(DataTreeChangeListenerActor.java:55)[171:org.opendaylight.controller.sal-distributed-datastore:1.4.0.SNAPSHOT]
at org.opendaylight.controller.cluster.datastore.DataTreeChangeListenerActor.handleReceive(DataTreeChangeListenerActor.java:37)[171:org.opendaylight.controller.sal-distributed-datastore:1.4.0.SNAPSHOT]
at org.opendaylight.controller.cluster.common.actor.AbstractUntypedActor.onReceive(AbstractUntypedActor.java:25)[166:org.opendaylight.controller.sal-clustering-commons:1.4.0.SNAPSHOT]
at akka.actor.UntypedActor$$anonfun$receive$1.applyOrElse(UntypedActor.scala:165)[154:com.typesafe.akka.actor:2.4.4]
at akka.actor.Actor$class.aroundReceive(Actor.scala:482)[154:com.typesafe.akka.actor:2.4.4]
at akka.actor.UntypedActor.aroundReceive(UntypedActor.scala:95)[154:com.typesafe.akka.actor:2.4.4]
at akka.actor.ActorCell.receiveMessage(ActorCell.scala:526)[154:com.typesafe.akka.actor:2.4.4]
at akka.actor.ActorCell.invoke(ActorCell.scala:495)[154:com.typesafe.akka.actor:2.4.4]
at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:257)[154:com.typesafe.akka.actor:2.4.4]
at akka.dispatch.Mailbox.run(Mailbox.scala:224)[154:com.typesafe.akka.actor:2.4.4]
at akka.dispatch.Mailbox.exec(Mailbox.scala:234)[154:com.typesafe.akka.actor:2.4.4]
at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)[150:org.scala-lang.scala-library:2.11.8.v20160304-115712-1706a37eb8]
at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)[150:org.scala-lang.scala-library:2.11.8.v20160304-115712-1706a37eb8]
at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)[150:org.scala-lang.scala-library:2.11.8.v20160304-115712-1706a37eb8]
at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)[150:org.scala-lang.scala-library:2.11.8.v20160304-115712-1706a37eb8]