Having the node window open spits out the error below when hitting play mode.

ShaderForge.SF_PassSettings.OnLocalGUI (Int32 yOffset, Int32 in_maxWidth)

ShaderForge.SF_Editor.DrawPreviewPanel (Rect r)

ShaderForge.SF_Editor.OnGUI ()

System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:222)