@Override
    public Object getSubstituteValue(final EntryEvent<K, V> event) {
      return new GatewayEventSubstituteObject(this, SUBSTITUTION_PREFIX + event.getKey());
    }
Regression test for TRAC #50366: NullPointerException with AsyncEventQueue#size() when number
of dispatchers is more than 1
geode-core/src/distributedTest/java/org/apache/geode/internal/cache/wan/asyncqueue/ConcurrentAsyncEventListenerDistributedTest.java