Failure in initialisation: java.lang.NullPointerException when connection-ref isn't configured properly

It's easy to reproduce, just edit A-MQ7-7.0.0.ER15-1-redhat-1/examples/features/ha/replicated-failback-static/src/main/resources/activemq/server1/broker.xml by replacing "connector-ref" attribute from:
<connector-ref>netty-connector</connector-ref>
to:
<connector-ref>netty-connector-blabla</connector-ref>

run mvn verify:
[bmachado@localhost replicated-failback-static] $ mvn verify

You will sill the NPE when the slave broker is started:

ReplicatedFailbackStaticExample1-out:16:33:18,405 ERROR [org.apache.activemq.artemis.core.server] AMQ224000: Failure in initialisation: java.lang.NullPointerException
ReplicatedFailbackStaticExample1-out: at org.apache.activemq.artemis.core.server.cluster.ClusterController.addClusterTopologyListenerForReplication(ClusterController.java:195) [artemis-server-1.5.1.amq-700002-redhat-1.jar:1.5.1.amq-700002-redhat-1]
ReplicatedFailbackStaticExample1-out: at org.apache.activemq.artemis.core.server.impl.SharedNothingBackupActivation.run(SharedNothingBackupActivation.java:137) [artemis-server-1.5.1.amq-700002-redhat-1.jar:1.5.1.amq-700002-redhat-1]
ReplicatedFailbackStaticExample1-out: at org.apache.activemq.artemis.core.server.impl.ActiveMQServerImpl$ActivationThread.run(ActiveMQServerImpl.java:2771) [artemis-server-1.5.1.amq-700002-redhat-1.jar:1.5.1.amq-700002-redhat-1]

It would be great to have an "attribute configuration exception" to make it easier to understand what was the incorrect attribute.