I have a github enterprise installation. I'm trying to get Jenkins connected to it. When I set up a repo and turn on 'GitHub hook trigger for GITScm polling', I see the hook get created in my repo, however it has a Red Triangle icon. Hovering over it says 'Invalid HTTP Reponse: 0'.

When I look at the Jenkins log, I see github tried to post an event, but I see the following error:

java.lang.NullPointerException
at org.jenkinsci.plugins.github.webhook.subscriber.DefaultPushGHEventSubscriber.onEvent(DefaultPushGHEventSubscriber.java:77)
at org.jenkinsci.plugins.github.extension.GHEventsSubscriber$4.applyNullSafe(GHEventsSubscriber.java:240)
at org.jenkinsci.plugins.github.extension.GHEventsSubscriber$4.applyNullSafe(GHEventsSubscriber.java:236)
at org.jenkinsci.plugins.github.util.misc.NullSafeFunction.apply(NullSafeFunction.java:18)
at com.google.common.collect.Iterators$8.next(Iterators.java:812)
at com.google.common.collect.Lists.newArrayList(Lists.java:139)
at com.google.common.collect.Lists.newArrayList(Lists.java:119)
at org.jenkinsci.plugins.github.util.FluentIterableWrapper.toList(FluentIterableWrapper.java:147)
at com.cloudbees.jenkins.GitHubWebHook.doIndex(GitHubWebHook.java:124)
at java.lang.invoke.MethodHandle.invokeWithArguments(MethodHandle.java:627)
at org.kohsuke.stapler.Function$MethodFunction.invoke(Function.java:343)
at org.jenkinsci.plugins.github.webhook.RequirePostWithGHHookPayload$Processor.invoke(RequirePostWithGHHookPayload.java:76)
at org.kohsuke.stapler.PreInvokeInterceptedFunction.invoke(PreInvokeInterceptedFunction.java:26)
at org.kohsuke.stapler.Function.bindAndInvoke(Function.java:184)
at org.kohsuke.stapler.Function.bindAndInvokeAndServeResponse(Function.java:117)
at org.kohsuke.stapler.IndexDispatcher.dispatch(IndexDispatcher.java:26)
at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:715)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:845)
at org.kohsuke.stapler.MetaClass$10.dispatch(MetaClass.java:374)
at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:715)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:845)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:649)
at org.kohsuke.stapler.Stapler.service(Stapler.java:238)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:812)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1669)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:135)
at hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:126)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
at com.cloudbees.jenkins.GitHubWebHookCrumbExclusion.process(GitHubWebHookCrumbExclusion.java:29)
at hudson.security.csrf.CrumbFilter.doFilter(CrumbFilter.java:58)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:84)
at hudson.security.UnwrapSecurityExceptionFilter.doFilter(UnwrapSecurityExceptionFilter.java:51)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at jenkins.security.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:117)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at org.acegisecurity.providers.anonymous.AnonymousProcessingFilter.doFilter(AnonymousProcessingFilter.java:125)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at org.acegisecurity.ui.rememberme.RememberMeProcessingFilter.doFilter(RememberMeProcessingFilter.java:135)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at org.acegisecurity.ui.AbstractProcessingFilter.doFilter(AbstractProcessingFilter.java:271)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at jenkins.security.BasicHeaderProcessor.doFilter(BasicHeaderProcessor.java:93)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at org.acegisecurity.context.HttpSessionContextIntegrationFilter.doFilter(HttpSessionContextIntegrationFilter.java:249)
at hudson.security.HttpSessionContextIntegrationFilter2.doFilter(HttpSessionContextIntegrationFilter2.java:67)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:76)
at hudson.security.HudsonFilter.doFilter(HudsonFilter.java:171)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
at org.kohsuke.stapler.compression.CompressionFilter.doFilter(CompressionFilter.java:49)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
at hudson.util.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:82)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
at org.kohsuke.stapler.DiagnosticThreadNameFilter.doFilter(DiagnosticThreadNameFilter.java:30)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:585)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143)
at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:553)
at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:223)
at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1127)
at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:515)
at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:185)
at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1061)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)
at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:97)
at org.eclipse.jetty.server.Server.handle(Server.java:499)
at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:311)
at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:257)
at org.eclipse.jetty.io.AbstractConnection$2.run(AbstractConnection.java:544)
at winstone.BoundedExecutorService$1.run(BoundedExecutorService.java:77)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)

Interestingly enough, if I take the same payload and put it in a JSON, I can post the even manually using curl:
$ curl -X POST --header "Content-Type: application/json" --header "X-GitHub-Event: push" -d @data.json http://XXX.XXX.XXX.XXX:8080/github-webhook/ -v

• About to connect() to proxy proxy-server port 8080 (#0)
• Trying XXX.XXX.XXX.XXX... connected
• Connected to proxy-server (XXX.XXX.XXX.XXX) port 8080 (#0)

POST http://XXX.XXX.XXX.XXX:8080/github-webhook/ HTTP/1.1
User-Agent: curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.18 Basic ECC zlib/1.2.3 libidn/1.18 libssh2/1.4.2
Host: XXX.XXX.XXX.XXX:8080
Accept: /
Proxy-Connection: Keep-Alive
Content-Type: application/json
X-GitHub-Event: push
Content-Length: 6983
Expect: 100-continue

< HTTP/1.1 100 Continue
< HTTP/1.1 200 OK
< Date: Sun, 19 Feb 2017 15:27:47 GMT
< X-Content-Type-Options: nosniff
< Content-Length: 0
< Server: Jetty(9.2.z-SNAPSHOT)
< Proxy-Connection: Keep-Alive
< Connection: Keep-Alive
<

• Connection #0 to host proxy-server left intact
• Closing connection #0

Looking at the code in org.jenkinsci.plugins.github.webhook.subscriber.DefaultPushGHEventSubscriber.onEvent(DefaultPushGHEventSubscriber.java:77), it looks like the call to getPusher is null.

In deed, when I put the json in a unit test, getPusher returns null.