Replace this:
'search' => ($auth->acl_get('u_search')) ? append_sid("{$phpbb_root_path}search.$phpEx", 'search_author=' . urlencode($row['username']) .'&sr=posts') : '',

With this:
'search' => ($auth->acl_get('u_search')) ? append_sid("{$phpbb_root_path}search.$phpEx", 'author=' . urlencode($row['username']) .'&sr=posts') : '',

And now it works.