SyntaxError: JSON.parse

I have a simple WS, made in php, everything was fine, I use it from an Android application, but for some time it has shown me an error when doing login, something that JSON is not consuming correctly because of this problem

and I get a blank space at the beginning of the json.

    {"Login":[{"RFC":"LOOF8910077G2","0":"LOOF8910077G2","CLAVE_TRABAJADOR":"189010016","1":"189010016","EMAIL":null,"2":null,"Nombre":"JOSE FRANCISCOLOPEZORTIZ","3":"JOSE FRANCISCOLOPEZORTIZ"}]}

and this is a piece of my PHP code

Query

public function login($control,$pass){
        try{
            $sql ="SELECT RFC, CLAVE_TRABAJADOR, EMAIL,(NOMBRE + PATERNO + MATERNO) AS Nombre FROM trabajad WHERE RFC = '$control' AND PWD = '$pass'";
                //$query = $this->con->query($sql);
                /*$data=Array();
                $query = sqlsrv_query($this->con,$sql);
                $row = sqlsrv_fetch_array($query);
                //$row = $query->fetch(PDO::FETCH_ASSOC);*/
                $stmt = $this->con->prepare($sql);
                $stmt->execute(); 
                $row = $stmt->fetch(PDO::FETCH_ASSOC);

                return $row;

            }catch(PDOException $e){
                echo $e->getMessage();
            }
        }//Fin login

and the code where I get the return of the query

header("Content-Type:application/json;charset=UTF-8");
$db = new Conexion;
$trabajador = new Trabajador($db);

$foto = $_POST['foto'];//Obtengo la imagen para guardarla en el servidor
//$foto = addslashes(file_get_contents($_FILES['foto']['tmp_name']));
$clave = $_POST['clave'];
$token = $_POST['token'];

switch ($_REQUEST['op']) {
    case 'login':
        //$rfc = isset($_GET['rfc']) ? limpiarCadena($_GET['rfc']):"";
        //$contra = isset($_GET['contra']) ? limpiarCadena($_GET['contra']):"";
    $rfc = $_GET['rfc'];
    $contra = $_GET['contra'];

    $respuesta = $trabajador->login($rfc,$contra);
    $data=Array();
    foreach ($respuesta as $elemento ) {
            $data["Login"][]=$elemento;
                # code.../
        }
    echo json_encode($data);
    /*if (!empty($respuesta)) {
            # code...

        foreach ($respuesta as $elemento ) {
            $data["Login"][]=$elemento;
                # code.../
        }
        echo json_encode($data);
    }else{
        echo json_encode("Mal");
    }*/
    break;