Upstream: https://we.phorge.it/T15164
Currently unassigned tasks will get the user executing the action assigned when the task is marked as resolved. If you do not want that so happen and remove yourself in the step, you'll get a warning message, that you one of your actions has no effect.
It would be really nice to at list have this message removed or suppressed in that use case. It's annoying and not quite correct in that case.
P.S.: Maybe this task will be invalid when [V22] will lead to removing the auto assignment in the first place.