when you run any search, there appears the table with results and in the last column there is "Last Post" with date of posting and the name of the author...this name is a hyperlink which should redirect you to the users profile...but in all those links there is empty "user_id" parameter so they leads nowhere (or on the error screen "No such a user")...

really no one marked this so far or is there any purpose why it is made so?

Fixed. Amazing that no one noticed it until now...