Remove unneeded event handling (handled elsewhere now)

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/Views/GraphEditorView.cs

             Add(content);
         }
 
-        List<INode> nodesToRemove = new List<INode>();
-        List<IEdge> edgesToRemove = new List<IEdge>();
-
-            if (graphViewChange.elementsToRemove != null)
-            {
-                m_Graph.owner.RegisterCompleteObjectUndo("Delete");
-                foreach (var element in graphViewChange.elementsToRemove)
-                {
-                    var nodeView = element as MaterialNodeView;
-                    if (nodeView != null && nodeView.node != null)
-                        nodesToRemove.Add(nodeView.node);
-
-                    var edgeView = element as Edge;
-                    if (edgeView != null)
-                    {
-                        var edge = edgeView.userData as IEdge;
-                        if (edge != null)
-                            edgesToRemove.Add(edge);
-                    }
-                }
-
-                m_Graph.RemoveElements(nodesToRemove, edgesToRemove);
-                graphViewChange.elementsToRemove.Clear();
-                nodesToRemove.Clear();
-                edgesToRemove.Clear();
-            }
-
-                    m_Graph.owner.RegisterCompleteObjectUndo("Connect Edge");
+                    {
+                        m_Graph.owner.RegisterCompleteObjectUndo("Connect Edge");
+                    }
                 }
                 graphViewChange.edgesToCreate.Clear();
             }
         Edge AddEdge(IEdge edge)
         {
             var sourceNode = m_Graph.GetNodeFromGuid(edge.outputSlot.nodeGuid);
+            if (sourceNode == null)
+            {
+                Debug.LogWarning("Source node is null");
+                return null;
+            }
+            if (targetNode == null)
+            {
+                Debug.LogWarning("Target node is null");
+                return null;
+            }
             var targetSlot = targetNode.FindInputSlot<MaterialSlot>(edge.inputSlot.slotId);
 
             var sourceNodeView = m_GraphView.nodes.ToList().OfType<MaterialNodeView>().FirstOrDefault(x => x.node == sourceNode);

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/Views/MaterialNodeView.cs

 
             m_GraphView = graphView;
             node = inNode;
+            persistenceKey = node.guid.ToString();
             UpdateTitle();
 
             m_ControlsContainer = new VisualElement