如何在'country_arab'中停止错误日志（非法字符串偏移）

please help me to stop error log it very big size and stop my server

if(isset($userdata_nor) && !empty($userdata_nor))
{
    foreach ($userdata_nor as $r) 
    {
        $str = $r['username'];
        $a = ucfirst($str[0]);
        if(preg_match('/[A-Za-z]/', $a)) {
           $image = LETTER_IMAGE.ucfirst($str[0]).".png";
        }
        else
        {
            $image = LETTER_IMAGE."ic_default_profile_pic.png";
        }

        $que2 = "SELECT * FROM `country` WHERE `country` = '".$r['country']."'";
        $data12 = $db->qry($que2,2);



        $country = $data12[0]['country_arab'];