NullPointerException on several "Manage Jenkins" pages

[MikeBerryFR]

After installing and successfully configuring the Slack-Notification-Plugin, we're seeing sporadic NPEs on various pages, particularly if the user session has expired:

Session expired, this NPE is displayed instead of the login page:

java.lang.NullPointerException
	at jenkins.plugins.slack.webhook.WebhookEndpoint.getUrlName(WebhookEndpoint.java:51)
	at jenkins.model.Jenkins.getDynamic(Jenkins.java:3642)
	at java.lang.invoke.MethodHandle.invokeWithArguments(MethodHandle.java:627)
	at org.kohsuke.stapler.Function$MethodFunction.invoke(Function.java:343)
	at org.kohsuke.stapler.Function.bindAndInvoke(Function.java:184)
	at org.kohsuke.stapler.MetaClass$10.dispatch(MetaClass.java:372)
	at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:715)

Global Tool Configuration, this NPE is displayed instead of the configuration page:

java.lang.NullPointerException
	at jenkins.plugins.slack.webhook.WebhookEndpoint.getUrlName(WebhookEndpoint.java:51)
	at jenkins.model.Jenkins.getUnprotectedRootActions(Jenkins.java:4681)
	at jenkins.model.Jenkins.isSubjectToMandatoryReadPermissionCheck(Jenkins.java:4653)
	at jenkins.model.Jenkins.getTarget(Jenkins.java:4631)
	at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:674)
	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:728)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
	at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:135)
	at hudson.plugins.greenballs.GreenBallFilter.doFilter(GreenBallFilter.java:59)
	at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:132)
	at hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:138)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
	at hudson.security.csrf.CrumbFilter.doFilter(CrumbFilter.java:49)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)

We're running Jenkins LTS v2.73.2 behind a Tomcat Manager

[MikeBerryFR]

Slack Outgoing Webhooks were intentionally left not configured under the global config as this is the unsupported legacy integration method for Slack.

Slack App integration was configured and working despite the errors above.

[sjqnn]

Seeing the same issue when certain things are left unconfigured. chat app integration plugins being left unconfigured should not crash jenkins....seems like this should be a higher priority.

[yixiaol-m]

We are seeing a similar issue that caused Jenkins to crash.
Just installed the plugin and didn't configure anything, Jenkins crashed about 30 minutes after the installation.

Dec 28, 2017 11:34:27 AM org.eclipse.jetty.util.log.JavaUtilLog warn
WARNING: Error while serving https://***/oa/ajaxBuildQueue
java.lang.reflect.InvocationTargetException
at org.kohsuke.stapler.Function$MethodFunction.invoke(Function.java:347)
at org.kohsuke.stapler.Function.bindAndInvoke(Function.java:184)
at org.kohsuke.stapler.MetaClass$10.dispatch(MetaClass.java:372)
at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:715)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:845)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:649)
at org.kohsuke.stapler.Stapler.service(Stapler.java:238)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:812)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1669)
at com.cloudbees.jenkins.ha.HAHealthCheckFilter.doFilter(HAHealthCheckFilter.java:35)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:135)
at org.jenkinsci.plugins.ssegateway.Endpoint$SSEListenChannelFilter.doFilter(Endpoint.java:225)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:132)
at com.cloudbees.jenkins.support.slowrequest.SlowRequestFilter.doFilter(SlowRequestFilter.java:37)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:132)
at io.jenkins.blueocean.auth.jwt.impl.JwtAuthenticationFilter.doFilter(JwtAuthenticationFilter.java:51)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:132)
at com.smartcodeltd.jenkinsci.plugin.assetbundler.filters.LessCSS.doFilter(LessCSS.java:47)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:132)
at
.....
Caused by: java.lang.NullPointerException
at jenkins.plugins.slack.webhook.WebhookEndpoint.getUrlName(WebhookEndpoint.java:51)
at jenkins.model.Jenkins.getDynamic(Jenkins.java:3621)
at java.lang.invoke.MethodHandle.invokeWithArguments(MethodHandle.java:627)
at org.kohsuke.stapler.Function$MethodFunction.invoke(Function.java:343)
... 82 more

[sebglon]

Same for me on 2.100 but nice after jenkinsn restart

[kmadel]

see #403