the following stage generates NPE, even when built against a PR:

stage ('mobileproduct - Prebuild') {

 githubPRComment comment: githubPRMessage('Build ${BUILD_NUMBER} ${BUILD_STATUS}')
}

the following NPE is generated:
java.lang.NullPointerException
at org.jenkinsci.plugins.github.pullrequest.utils.JobHelper.getGhRepositoryFromPRTrigger(JobHelper.java:161)
at org.jenkinsci.plugins.github.pullrequest.utils.JobHelper.getGhPullRequest(JobHelper.java:177)
at org.jenkinsci.plugins.github.pullrequest.publishers.impl.GitHubPRCommentPublisher.perform(GitHubPRCommentPublisher.java:73)
at org.jenkinsci.plugins.workflow.steps.CoreStep$Execution.run(CoreStep.java:80)
at org.jenkinsci.plugins.workflow.steps.CoreStep$Execution.run(CoreStep.java:67)
at org.jenkinsci.plugins.workflow.steps.SynchronousNonBlockingStepExecution.lambda$start$0(SynchronousNonBlockingStepExecution.java:47)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
Finished: FAILURE

the checkout phase checks out multiple projects, even though I am not sure it's supposed to matter.