exception when running PerfExample2 with error args:
Exception in thread "main" java.lang.NullPointerException
at com.baidu.hugegraph.event.EventHub.destroy(EventHub.java:80)
at com.baidu.hugegraph.HugeGraph.shutdown(HugeGraph.java:570)
at com.baidu.hugegraph.example.PerfExample2.main(PerfExample2.java:44)
exception when running PerfExample2 with error args: