PHP - Notice: Trying to get property of non-object

<?php header('Access-Control-Allow-Origin: *'); ?>

<?php header('Access-Control-Allow-headers: Origin, X-Requested-with, content-type,accept');?>

<?php header('Access-Control-Allow-methods: POST, GET, OPTIONS, PUT');?>

<?php

//mysqli

$con = mysqli_connect('localhost', 'root', '', 'Base_Datos_Final');

$data = json_decode(file_get_contents("php://input"));

$ucorreo = mysqli_real_escape_string($con, $data->correo);

$unombre = mysqli_real_escape_string($con, $data->nombre);

$uapellido = mysqli_real_escape_string($con, $data->apellido);

$utelefono = mysqli_real_escape_string($con, $data->telefono);

$ucontrasena = mysqli_real_escape_string($con, $data->contrasena);

$clave = md5($ucontrasena);

$ucreado = mysqli_real_escape_string($con, $data->creado);

$ulatitud = mysqli_real_escape_string($con, $data->latitud);

$ulongitud = mysqli_real_escape_string($con, $data->longitud);

if (!empty($ucorreo)) {

$qry_em = 'select count(*) as cnt from Usuarios where Correo ="' . $ucorreo . '"';

$qry_res = mysqli_query($con,$qry_em);

$res = mysqli_fetch_assoc($qry_res);

if ($res['cnt'] == 0) {

    $qry = 'INSERT INTO Usuarios VALUES (null, "' . $ucorreo . '","' . $unombre . '","' . $uapellido . '","' . $utelefono . '","' . $clave . '","' . $ucreado . '","' . $ulatitud . '","' . $ulongitud . '")';

    $qry_res = mysqli_query($qry);

    if ($qry_res) {

        $arr = array('msg' => "usuario creado!!!", 'error' => '');

        $jsn = json_encode($arr);

        print_r($jsn);

    } else {

        $arr = array('msg' => "", 'error' => 'error insertando');

        $jsn = json_encode($arr);

        print_r($jsn);

    }

} else {

    $arr = array('msg' => "", 'error' => 'usuario ya existe');

    $jsn = json_encode($arr);

    print_r($jsn);

}

}

?>

.controller('registroCtrl',function($http,$ionicPopup,$scope){

 $scope.errors = [];

 $scope.msgs =[];

 $scope.inscribir = function(){

    $scope.errors.splice(0,$scope.errors.length);

      $scope.msgs.splice(0,$scope.msgs.length);

      $http.post('http://http://127.0.0.1/insertarIonic/insertar.php',

      {

            'correo': $scope.ucorreo,

            'nombre' :$scope.unombre,

            'apellido':$scope.uapellido,

            'telefono':$scope.utelefono,

            'contrasena':$scope.ucontrasena,

            'creado':$scope.ucreado,

            'latitud':$scope.ulatitud,

            'longitud':$scope.ulongitud,

      }).success(function(data,status,header,config){

               if(data.msg!= ''){

                $scope.msgs.push(data.msg);

                  $scope.showAlert = function() {

                    var alertPopup = $ionicPopup.alert({

                      title: $scope.unombre,

                      template: 'Te has registrado con exito',

                      cssClass: 'dark',

                      okType: 'button-energized'

                    });

                  };

                  $scope.showAlert();

                  //Aqui poner llamado a inicio

              }else{

               $scope.errors.push(data.error);

              }

          }).error(function(){

        $scope.msgs.push(data.status);

      });

}})