Steps to reproduce:

1. Open a thread discussion page (a page listing various threads, example: [1])
2. Click the "change subject" link at the top of a thread.
3. The title/subject is now editable. Click "save" without editing.

Expected results:

Since nothing has been changed, the action shouldn't be logged anywhere.

Actual resutls:

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.

[1] https://www.mediawiki.org/wiki/LiquidThreads_Test_Page

Version: master
Severity: normal
URL: https://www.mediawiki.org/w/index.php?title=Thread:LiquidThreads_Test_Page/Test_LQT_again&lqt_method=thread_history