如何修复 MySQLi 中的'在非对象上调用成员函数 fetch_assoc()”错误？

function get_recent_highs($view_deleted_images = false)
{
    $lower = $this->database->conn->real_escape_string($this->page_size * ($this->page_number - 1));
    $query = "SELECT image_id, date_uploaded FROM `images` ORDER BY ((SELECT SUM( image_id=`images`.image_id ) FROM `image_votes` AS score) / (SELECT DATEDIFF( NOW( ) , date_uploaded ) AS diff)) DESC LIMIT " . $this->page_size . " OFFSET $lower";
    $result = $this->database->query($query);

    if (!$result) {
        throw new Exception("Database Error [{$this->database->errno}] {$this->database->error}");
    }

    $page = array();
    while($row = $result->fetch_assoc())
    {
        try
        {
            array_push($page, new Image($row['image_id'], $view_deleted_images));
        }
        catch(ImageNotFoundException $e)
        {
            throw $e;
        }
    }

    return $page;
}