DNS_PING#destroy could yield NPE hiding the root cause

Caused by: java.lang.NullPointerException
at org.jgroups.protocols.dns.DNS_PING.destroy(DNS_PING.java:70)
at java.util.ArrayList.forEach(ArrayList.java:1257)
at org.jgroups.stack.ProtocolStack.destroy(ProtocolStack.java:876)
at org.jgroups.stack.ProtocolStack.initProtocolStack(ProtocolStack.java:867)
at org.jgroups.stack.ProtocolStack.init(ProtocolStack.java:849)
at org.jgroups.JChannel.<init>(JChannel.java:155)
at org.jboss.as.clustering.jgroups.JChannelFactory.createChannel(JChannelFactory.java:116)
at org.jboss.as.clustering.jgroups.subsystem.ChannelServiceConfigurator.get(ChannelServiceConfigurator.java:96)