When this error happens in your Tortoise SVN Commit screen as shown below, then it means (I assume) that some time back that user had svn-locked that file and later deleted from SVN by using keep-lock in svn commit window (or in somewhere the keep-lock played badly).
How to fix it then?
Go to the logs of that folder in which that the file was locked as explained in error message above (in my case, I went to UserAccountAuthentication logs). Look for the file in one of the recent revision as below, right click and choose “Browse repository”.
This should bring up the repo version when that file existed in repo. In the repo browser, right click that error file and choose the “Break Lock”. This should break the lock of that file even if some user had locked it.
Then try to commit, it should commit perfectly as below. If the error shows up again, it should be some other file and ensure to do the same process above.