Fix for serialized selection

MaterialGraphProject/Assets/GraphFramework/SerializableGraph/Editor/Drawing/SerializableGraphView.cs

             var selectedDrawers = graphDataSource.graphAsset.drawingData.selection
                 .Select(guid => contentViewContainer.children
                             .OfType<NodeDrawer>()
-                            .FirstOrDefault(drawer => ((NodeDrawData) drawer.dataProvider).node.guid == guid));
+                            .FirstOrDefault(drawer => ((NodeDrawData) drawer.dataProvider).node.guid == guid))
+                .ToList();
 
             foreach (var drawer in selectedDrawers)
                 AddToSelection(drawer);

MaterialGraphProject/Assets/GraphFramework/SerializableGraph/Editor/Drawing/Manipulators/NodeExpander.cs.meta

-fileFormatVersion: 2
-guid: 1e2e1c761ebf4ce478e48e37c5b95ddb
-timeCreated: 1478596127
-licenseType: Pro
-MonoImporter:
-  serializedVersion: 2
-  defaultReferences: []
-  executionOrder: 0
-  icon: {instanceID: 0}
-  userData: 
-  assetBundleName: 
-  assetBundleVariant: