[FIX] #157 Removed the check for Master node which casued the Exception.

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/MaterialGraphEditWindow.cs

             if (graph == null)
                 return;
 
-            List<PropertyCollector.TextureInfo> configuredTextures;
-            graph.GetShader(Path.GetFileNameWithoutExtension(path), GenerationMode.ForReals, out configuredTextures);
-
             var shaderImporter = AssetImporter.GetAtPath(path) as ShaderGraphImporter;
             if (shaderImporter == null)
                 return;

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Importers/ShaderGraphImporter.cs

         var text = GetShaderText<MaterialGraph>(ctx.assetPath, out configuredTextures);
         if (text == null)
             text = errorShader;
+        
+        var name = Path.GetFileNameWithoutExtension(ctx.assetPath);
+        string shaderName = string.Format("graphs/{0}", name);
+        text = text.Replace("Hidden/GraphErrorShader2", shaderName);
 
         var shader = ShaderUtil.CreateShaderAsset(text);