Непонятная ошибка: Call to a member function selectRow() on null

<?php
if (!defined('IS_IN_ENGINE'))
{
    header('HTTP/1.1 403 Forbidden');
    die('<h1>403 Forbidden</h1>');
}
 
global $config;
$ajax = isset($_SERVER['HTTP_X_REQUESTED_WITH']);
 
if (!isset($_SESSION['randomHash']))
{
    $randomHash = md5(generateRandomString(11, 15));
    $_SESSION['randomHash'] = $randomHash;
}
else
{
    $randomHash = $_SESSION['randomHash'];
}
 
$errors = array();
$status = 'success';
if (isset($_POST['username']) && isset($_POST['email']) && $ajax)
{
    sleep(1);
    $realm = isset($_POST['realm']) ? $_POST['realm'] : 0;
    $realmType = $config['realms'][$realm]['type'];
 
    if ($_POST['r_randomhash'] != $randomHash)
        $errors[] = $lang['need_reload'];
    if ($_POST['username'] == '' || $_POST['username'] == $lang['username'])
        $errors[] = $lang['no_username'];
    if ($_POST['email'] == '' || $_POST['email'] == 'email')
        $errors[] = $lang['no_email'];
 
    if (empty($errors))
    {
        global $rDB;
 
        $accInfo = $rDB[$realm]->selectRow(GetQueryByRealmType($realmType, QUERY_GET_ACCINFO_BY_NAME), PrepareString($_POST['username']));
        if (!$accInfo || strtolower(PrepareString($_POST['email'])) != strtolower($accInfo['email']))
            $errors[] = $lang['rest_unknown_user'];
 
        if (empty($errors))
        {
            $hash = buildConfirmationHash(CONFIRM_RESTORE_PASSWORD, $realm, $accInfo['id']);
            if ($hash != CONFIRM_ERROR)
            {
                $smarty->assign('username', $accInfo['username']);
                $smarty->assign('restore_link', $config['website']['baseurl'] .
                        'hash/' . $hash . '/');
                $smarty->assign('servername', $config['website']['server_name']);
                $smarty->assign('realmlist', $config['realms'][$realm]['realmlist']);
                $smarty->assign('server_url', $config['website']['baseurl']);
                $emailtext = $smarty->fetch('mail_templates/' .
                        $config['realms'][$realm]['mail_template'] . '/restorepass.tpl');
                if (!@SendEmail($accInfo['email'], $lang['rest_mail_title'], $emailtext, 1))
                    $status = 'fail_email';
            }
        }
    }
}
 
$smarty->assign('errors', $errors);
 
if ($ajax)
{
    if (!empty($errors))
        $smarty->display('login_ajax.tpl');
    else
        echo $status;
    exit;
}
 
$page['Title'] = $lang['restore_title'];
$page['frmact'] = $config['website']['userlogin'];
$smarty->assign('page', $page);
$smarty->assign('restore_random', $randomHash);
$smarty->display('restore.tpl');
?>

$accInfo = $rDB[$realm]->selectRow(GetQueryByRealmType($realmType, QUERY_GET_ACCINFO_BY_NAME), PrepareString($_POST['username']));