Steps to reproduce:
- Open a thread discussion page (a page listing various threads, example: )
- Click the "change subject" link at the top of a thread.
- The title/subject is now editable. Click "save" without editing.
Since nothing has been changed, the action shouldn't be logged anywhere.
The action has been logged in the thread history (see URL)
Note that adding only spaces at the start or end of the subject should not trigger a change subject log neither. Subject should be trim()-ed before saved.