While it is nice that with PrioritySorter 2.5.1 and JENKINS-44014 fixed there are no issues anymore with exceptions, it still does not sort PlaceholderTasks in all cases. The getPriority() in PriorityConfigurationPlaceholderTaskHelper only logs a warning and uses a default configuration. However, any PlaceholderTask belongs to a Run, which belongs to a  Job. So in case ownerTask is null, task.run().getParent() or task.runForDisplay().getParent() could be used instead.

Related: JENKINS-45028.