Fix issue causing deserialization to fail

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Data/Nodes/MasterNode.cs

                 return; 
 
             m_SubShaders.Add(subshader);
-            onModified(this, ModificationScope.Node);
+            Dirty(ModificationScope.Node);
-            onModified(this, ModificationScope.Node);
+            Dirty(ModificationScope.Node);
         }
 
         public string GetShader(GenerationMode mode, string outputName, out List<PropertyCollector.TextureInfo> configuredTextures)