function getUserAvatarUrl($userId) {
    $userId = intval($userId);
    if ($userId <= 0) return null;

    $rsUser = CUser::GetByID($userId);
    $arUser = $rsUser->Fetch();

    if (!$arUser || empty($arUser['PERSONAL_PHOTO'])) return null;

    $imgId = intval($arUser['PERSONAL_PHOTO']);
    if ($imgId <= 0) return null;

    return CFile::GetPath($imgId) ?: null;
}