I tried to use the github status notification post build action on a job that is triggered by a manually configured remote URL (and not by a standard github push trigger). The GitHubCommitNotifier class does not expect this and crashes when querying the push trigger.

java.lang.NullPointerException
at com.cloudbees.jenkins.GitHubCommitNotifier.perform(GitHubCommitNotifier.java:52)
at hudson.tasks.BuildStepMonitor$1.perform(BuildStepMonitor.java:19)
at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:804)
at hudson.model.AbstractBuild$AbstractBuildExecution.performAllBuildSteps(AbstractBuild.java:776)
at hudson.model.Build$BuildExecution.post2(Build.java:183)
at hudson.model.AbstractBuild$AbstractBuildExecution.post(AbstractBuild.java:726)
at hudson.model.Run.execute(Run.java:1601)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:46)
at hudson.model.ResourceController.execute(ResourceController.java:88)
at hudson.model.Executor.run(Executor.java:241)