Error when Reverse Engineering (#80)

I reverse engineered my .vbproj successfully the first time, but then I wanted to redo it, so I closed the old project without saving. When I go to Tools -> Reverse Engineering -> Source Code, change to VB.NET, add my project, it takes awhile and completes the progress bar. Then I get the following error with options to Exit Application or Continue.

System.NullReferenceException: Object reference not set to an instance of an object.

at SoftwareIdeasModeler.Diagrams.UmlDiagrams.UmlDiagram..ctor(Model model)

at SoftwareIdeasModeler.Diagrams.UmlDiagrams.UmlClassDiagram..ctor(Model model)

at SoftwareIdeasModeler.Dialogs.Importing.SourceCode.ImportForm.okButton_Click(Object sender, EventArgs e)

at System.Windows.Forms.Control.OnClick(EventArgs e)

at System.Windows.Forms.Button.OnClick(EventArgs e)

at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)

at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)

at System.Windows.Forms.Control.WndProc(Message& m)

at System.Windows.Forms.ButtonBase.WndProc(Message& m)

at System.Windows.Forms.Button.WndProc(Message& m)

at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)

at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)

at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)