Object reference not set to an instance of an object.

   at lambda_method(Closure , GenericRichTextViewModel )
   at Glass.Mapper.Sc.GlassHtml.MakeEditable[T](Expression`1 field, Expression`1 standardOutput, T model, Object parameters, Context context, Database database, TextWriter writer) in c:\TeamCity\buildAgent\work\8567e2ba106d3992\Source\Glass.Mapper.Sc\GlassHtml.cs:line 616