Cann`t draw node with specified coordinates on gViewer.

Try to using code from this question Change Node position in MSAGL , but it don`t works.

        Form form = new ();
        GViewer viewer = new ();
        Graph graph = new ("graph");
        graph.AddNode("test");
        Microsoft.Msagl.Core.Geometry.Point position = new(100, 100);
        graph.FindGeometryNode("test").Center = position;//exception in this line
        viewer.NeedToCalculateLayout = false; 
        viewer.Graph = graph;
        form.SuspendLayout();
        viewer.Dock = System.Windows.Forms.DockStyle.Fill;
        form.Controls.Add(viewer);
        form.ShowDialog();

It throwing NullReferenceException.

Message:

        "Object reference not set to an instance of an object." 

Stack:

MsaglTestApplication.dll!MsaglTestApplication.Program.Main() Line 23 C#