Jenkins version: 2.204.6

Jenkins is running directly

Its installed manually by unpacking the war file 

Its behind an nginx proxy

Using chrome

The issue just appeared when we switched our builds trigger from pollSCM to p4 triggers. The way we do this is that we have setup triggers in p4 which invoke a script, and in that script depending on the path of the changed file we calculate which job needs to run and which branch and we post to our jenkins URL. It works very nicely, but just noticed this NPE appearing in the logs. In case of failed builds we were not getting Failed emails with culprits 

which prompted a lookup in the logs and we found this:
2021-03-23 18:29:12.838+0000 [id=258084]    WARNING h.p.e.ExtendedEmailPublisher#sendMail: Could not send email.
java.lang.NullPointerException
    at jenkins.scm.RunWithSCM.calculateCulprits(RunWithSCM.java:136)
    at jenkins.scm.RunWithSCM.getCulprits(RunWithSCM.java:95)
    at org.jenkinsci.plugins.workflow.job.WorkflowRun.getCulprits(WorkflowRun.java:839)
    at jenkins.scm.RunWithSCM.calculateCulprits(RunWithSCM.java:132)
    at jenkins.scm.RunWithSCM.getCulprits(RunWithSCM.java:95)
    at org.jenkinsci.plugins.workflow.job.WorkflowRun.getCulprits(WorkflowRun.java:839)
    at jenkins.scm.RunWithSCM.calculateCulprits(RunWithSCM.java:132)
    at jenkins.scm.RunWithSCM.getCulprits(RunWithSCM.java:95)
    at org.jenkinsci.plugins.workflow.job.WorkflowRun.getCulprits(WorkflowRun.java:839)
    at hudson.plugins.emailext.plugins.recipients.CulpritsRecipientProvider.addRecipients(CulpritsRecipientProvider.java:59)
    at hudson.plugins.emailext.ExtendedEmailPublisher.createMail(ExtendedEmailPublisher.java:793)
    at hudson.plugins.emailext.ExtendedEmailPublisher.sendMail(ExtendedEmailPublisher.java:451)
    at hudson.plugins.emailext.EmailExtStep$EmailExtStepExecution.run(EmailExtStep.java:236)
    at hudson.plugins.emailext.EmailExtStep$EmailExtStepExecution.run(EmailExtStep.java:174)
    at org.jenkinsci.plugins.workflow.steps.AbstractSynchronousNonBlockingStepExecution$1$1.call(AbstractSynchronousNonBlockingStepExecution.java:47)
    at hudson.security.ACL.impersonate(ACL.java:290)
    at org.jenkinsci.plugins.workflow.steps.AbstractSynchronousNonBlockingStepExecution$1.run(AbstractSynchronousNonBlockingStepExecution.java:44)
    at java.util.concurrent.Executors$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)