Выдаёт ошибку Call to a member function fetch_assoc()

Question

Fatal error: Uncaught Error: Call to a member function fetch_assoc() on boolean in C:\OpenServer\domains\Diplom\php\checkdata.php:8 Stack trace: #0 {main} thrown in C:\OpenServer\domains\Diplom\php\checkdata.php on line 8

Не могу найти ошибку.

<?php
        $login = filter_var(trim($_POST['login']),
         FILTER_SANITIZE_STRING);
    $pass = filter_var(trim($_POST['psw']),
         FILTER_SANITIZE_STRING);
    $mysql = new mysqli('localhost', 'root', 'root', 'diplom');
    $result = $mysql->query("SELECT * FROM `user` WHERE `login` = '$login' AND `pass` = '$pass'");
    $user = $result->fetch_assoc();
    if(count($user) == 0){
        echo "Такого пользователя нету";
        exit();
    }
    print_r($user);
    exit(); 
    $mysql->close();
    header('Location: /');
    ?>