Just a minor bug, which may potentially happen due to the race condition if a task is being executed with SYSTEM authentication.

• UserInterruption#getUser() uses User.get(String), which creates users on demand.
• When we create CauseOfInterruption.UserInterruption, we expect it exists
• BUT: the user may be deleted from parallel thread by the time we call UserInterruption#print, which invokes getUser()
• In such case the recently deleted user will be recreated