... org.jenkinsci.plugins.github.extension.GHEventsSubscriber$4 applyNullSafe
SEVERE: Subscriber org.jenkinsci.plugins.github.webhook.subscriber.PingGHEventSubscriber failed to process PING hook, skipping...
net.sf.json.JSONException: null object
	at net.sf.json.JSONObject.verifyIsNull(JSONObject.java:2688)
	at net.sf.json.JSONObject.getString(JSONObject.java:2035)
	at org.jenkinsci.plugins.github.webhook.subscriber.PingGHEventSubscriber.onEvent(PingGHEventSubscriber.java:56)
	at org.jenkinsci.plugins.github.extension.GHEventsSubscriber$4.applyNullSafe(GHEventsSubscriber.java:134)
	at org.jenkinsci.plugins.github.extension.GHEventsSubscriber$4.applyNullSafe(GHEventsSubscriber.java:130)
	at org.jenkinsci.plugins.github.util.misc.NullSafeFunction.apply(NullSafeFunction.java:18)
	at com.google.common.collect.Iterators$8.next(Iterators.java:812)
	at com.google.common.collect.Lists.newArrayList(Lists.java:139)
	at com.google.common.collect.Lists.newArrayList(Lists.java:119)
	at org.jenkinsci.plugins.github.util.FluentIterableWrapper.toList(FluentIterableWrapper.java:137)
	at com.cloudbees.jenkins.GitHubWebHook.doIndex(GitHubWebHook.java:96)