Fix issues that should have caused compile errors

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Data/SubGraph/AbstractSubGraph.cs

         , IGeneratesBodyCode
         , IGeneratesFunction
     {
-        public virtual IEnumerable<AbstractMaterialNode> activeNodes { get; }
+        public virtual IEnumerable<AbstractMaterialNode> activeNodes { get { return Enumerable.Empty<AbstractMaterialNode>(); } }
 
         public PreviewMode previewMode
         {

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Data/SubGraph/AbstractSubGraphNode.cs

         , IMayRequireTime
     {
 
-        protected virtual AbstractSubGraph referencedGraph { get; }
+        protected abstract AbstractSubGraph referencedGraph { get; }
 
         public override bool hasPreview
         {

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/Inspector/ShaderLayerview.cs

 {
     public class ShaderLayerView : VisualElement
     {
-        public LayeredShaderGraph graph { get; }
-        public LayeredShaderGraph.Layer layer { get; }
+        public LayeredShaderGraph graph { get; private set; }
+        public LayeredShaderGraph.Layer layer { get; private set; }
 
         public ShaderLayerView(LayeredShaderGraph graph, LayeredShaderGraph.Layer layer)
         {

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

         SerializableGraphObject m_GraphObject;
 
         GraphEditorView m_GraphEditorView;
+
         GraphEditorView graphEditorView
         {
             get { return m_GraphEditorView; }
         {
             get { return m_GraphObject; }
             set
-        {
+            {
                 if (m_GraphObject != null)
                     DestroyImmediate(m_GraphObject);
                 m_GraphObject = value;
             var e = Event.current;
 
             if (e.type == EventType.ValidateCommand && (
-                    e.commandName == "Copy" && presenter.canCopy
-                    || e.commandName == "Paste" && presenter.canPaste
-                    || e.commandName == "Duplicate" && presenter.canDuplicate
-                    || e.commandName == "Cut" && presenter.canCut
-                    || (e.commandName == "Delete" || e.commandName == "SoftDelete") && presenter.canDelete))
+                e.commandName == "Copy" && presenter.canCopy
+                || e.commandName == "Paste" && presenter.canPaste
+                || e.commandName == "Duplicate" && presenter.canDuplicate
+                || e.commandName == "Cut" && presenter.canCut
+                || (e.commandName == "Delete" || e.commandName == "SoftDelete") && presenter.canDelete))
             {
                 e.Use();
             }
                     var inputSlotRef = new SlotReference(remappedInputNodeGuid, inputSlot.slotId);
                     graph.Connect(outputSlotRef, inputSlotRef);
                 }
+
                 // one edge needs to go to outside world
                 else if (outputRemapExists)
                 {
             var uniqueInputEdges = onlyOutputInternallyConnected.GroupBy(
                 edge => edge.outputSlot,
                 edge => edge,
-                (key, edges) => new {slotRef = key, edges = edges.ToList()});
+                (key, edges) => new { slotRef = key, edges = edges.ToList() });
             foreach (var group in uniqueInputEdges)
             {
                 var sr = group.slotRef;
             var uniqueOutputEdges = onlyInputInternallyConnected.GroupBy(
                 edge => edge.inputSlot,
                 edge => edge,
-                (key, edges) => new {slot = key, edges = edges.ToList()});
+                (key, edges) => new { slot = key, edges = edges.ToList() });
 
             var outputsNeedingConnection = new List<KeyValuePair<IEdge, IEdge>>();
             foreach (var group in uniqueOutputEdges)
             graphPresenter.graph.AddNode(subGraphNode);
             subGraphNode.subGraphAsset = subGraph;
 
-          /*  foreach (var edgeMap in inputsNeedingConnection)
-            {
-                graphPresenter.graph.Connect(edgeMap.Key.outputSlot, new SlotReference(subGraphNode.guid, edgeMap.Value.outputSlot.slotId));
-            }*/
+            /*  foreach (var edgeMap in inputsNeedingConnection)
+              {
+                  graphPresenter.graph.Connect(edgeMap.Key.outputSlot, new SlotReference(subGraphNode.guid, edgeMap.Value.outputSlot.slotId));
+              }*/
 
             foreach (var edgeMap in outputsNeedingConnection)
             {
             shaderImporter.SaveAndReimport();
             AssetDatabase.ImportAsset(path);
         }
-
 
         public void ChangeSelection(Object newSelection, Type graphType)
         {