[TECHNICAL-SUPPORT] LPS-25775 Current user's display language is changing automatically while editing other users

Hi Tamás,

We should change the display languageId only if the user edits itself. Otherwise, it's an unnecessary & annoying change.
We already have a similar approach for the "oldScreenName" variable in the updateUser method:

    if (oldScreenName.equals(user.getScreenName())) {
        oldScreenName = StringPool.BLANK;
    }

This is because the processAction method expects to get null or not null strings and performs further actions based on these values (from line 164).

This branch has a HEAD where I was able to test & reproduce the issue. The edit user functions are broken in the current trunk, but the issue still persists.

Here is a rebased branch: https://github.com/lipusz/liferay-portal/tree/LPS-25775-rebased