Empty PHP/SQL response when using ñ

Question

i'm making a request to my db.

When i change "Canuelas" to "Cañuelas", the response it's empty, i tried to change the db, table and row collation but no results.

Here it's an image of the empty response:

Here it's the php code i use to the request:

<?php
include "_db.php";
$con = crearConexion();

if ($con->connect_error) {
    die("Connection failed: " . $con->connect_error);
}

$postdata = file_get_contents("php://input");
$request = json_decode($postdata,true);

$action = $request['action'];

if ($action === "get_propiedades") {

    $consulta_propiedades = "SELECT * FROM propiedades WHERE quitado = ''";
    $result_propiedades = mysqli_query($con, $consulta_propiedades);

    $row_container_propiedades = array();

    while($row_propiedades = mysqli_fetch_array($result_propiedades)){
        array_push($row_container_propiedades, $row_propiedades);
    }

    $row_container_propiedades = json_encode($row_container_propiedades);

    echo $row_container_propiedades;
}else if ($action === "get_filtros") {

    $consulta_filtros = "SELECT * FROM filtros";
    $result_filtros = mysqli_query($con, $consulta_filtros);

    $row_container_filtros = array();

    while($row_filtros = mysqli_fetch_array($result_filtros)){
        array_push($row_container_filtros, $row_filtros);
    }

    $row_container_filtros = json_encode($row_container_filtros);

    echo $row_container_filtros;
}

$con->close();
?>

Note: The problem it's in "get_filtros". "get_propiedades" it's retrieved correctly.

Sorry for my bad english!

EDIT: The set_charset('utf8mb4'); did the magic, all i needed to do was adding that line to the db connection, here it's the db connection file if someone need it.

<?php
function crearConexion(){
    //Datos para la conexión con el servidor
    $servidor   = "localhost";
    $nombreBD   = "dbname";
    $usuario    = "dbuser";
    $contrasena = "dbpass";
    //Creando la conexión, nuevo objeto mysqli
    $conexion = new mysqli($servidor,$usuario,$contrasena,$nombreBD);
    $conexion->set_charset('utf8mb4'); 
    //Si sucede algún error la función muere e imprimir el error
    if($conexion->connect_error){
        die("Error en la conexion : ".$conexion->connect_errno.
                                  "-".$conexion->connect_error);
    }
    //Si nada sucede retornamos la conexión
    return $conexion;
}
?>