Running LayoutViewer problem

[kenjiuno]

When launch LayoutViewer from Visual Studio 2019, there is a System.NullReferenceException: 'Object reference not set to an instance of an object.' thrown.

Some ways to run from command line:

• Run dotnet run at OpenKh\OpenKh.Tools.LayoutViewer folder.
  For example: H:\Proj\OpenKh\OpenKh.Tools.LayoutViewer>dotnet run
• Run dotnet OpenKh.Tools.LayoutViewer.dll at bin\Debug\netcoreapp3.1
  For example: H:\Proj\OpenKh\OpenKh.Tools.LayoutViewer\bin\Debug\netcoreapp3.1>dotnet OpenKh.Tools.LayoutViewer.dll
• Copy OpenKh.Tools.LayoutViewer.dll.config to OpenKh.Tools.LayoutViewer.exe.config done at bin\Debug\netcoreapp3.1 folder,
  For example: H:\Proj\OpenKh\OpenKh.Tools.LayoutViewer\bin\Debug\netcoreapp3.1>copy OpenKh.Tools.LayoutViewer.dll.config OpenKh.Tools.LayoutViewer.exe.config

[kenjiuno]

Putting DefaultSettingValue also works...

        [global::System.Configuration.DefaultSettingValue("Magenta")]
        public global::System.Drawing.Color BackgroundColor {

The default value of BackgroundColor is filled at App.config: https://github.com/Xeeynamo/OpenKh/blob/a8de1e5cbc847b7ee87a16e29182f806d5b34e07/OpenKh.Tools.LayoutViewer/App.config#L14