Object reference not set to an instance of an object

After I just added the package, I ran it directly and reported this error. No matter how you adjust it, it won't work，The code is as follows：

string html = @"<!DOCTYPE html>
                <html lang=""en"">
                <head>
                    <meta charset=""UTF-8"">
                    <meta name=""viewport"" content=""width=device-width, initial-scale=1.0"">
                    <title>Document</title>
                </head>
                <body>
                    <h1>标题一</h1>
                    <img src=""https://file.ejiang.com:9001/childplat/resource/courseware/cover/9a2579ef-22af-4d9d-bd1a-5814df5107ca.jpg?size=m480"" />
                </body>
                </html>";
            Document.Create(container =>
            {
                container.Page(page =>
                {
                    page.Content().Column(col =>
                    {
                        col.Item().HTML(handler =>
                        {
                            handler.SetHtml(html);
                        });
                    });
                });
            }).GeneratePdf("123.pdf");
            Console.WriteLine("OK");

Relorer / HTMLToQPDF

Object reference not set to an instance of an object #11