[Cherrypick] DYN-10098: Dynamo Pan/Zoom gives CER crash (#16891) (#16928)

Co-authored-by: Jason <jasonstratton@users.noreply.github.com>

Author: zeusongit

src/DynamoCore/Graph/Nodes/CodeBlockNode.cs

@@ -1155,7 +1155,8 @@ private void LoadAndCreateConnectors(OrderedDictionary inportConnections, Ordere
                                 i);
                             //during an undo operation we should set the new input connector
                             //to have the same id as the old connector.
-                            if (context == SaveContext.Undo)
+                            // Null check: Make() returns null if port indices are no longer valid
+                            if (context == SaveContext.Undo && connector != null)
                             {
                                 connector.GUID = oldConnector.GUID;
                             }
@@ -1209,7 +1210,8 @@ private void LoadAndCreateConnectors(OrderedDictionary inportConnections, Ordere
 
                         // During an undo operation we should set the new output connector
                         // to have the same id as the old connector.
-                        if (context == SaveContext.Undo)
+                        // Null check: Make() returns null if port indices are no longer valid
+                        if (context == SaveContext.Undo && connector != null)
                         {
                             connector.GUID = oldConnector.GUID;
                         }

src/DynamoCoreWpf/Views/Core/WorkspaceView.xaml.cs

@@ -723,7 +723,6 @@ private void ClearNodeViewCache()
         private void UpdateNodeViewCacheScale()
         {
             var nodes = this.ChildrenOfType<NodeView>();
-            BitmapCache sharedCache = null;
             foreach (var node in nodes)
             {
                 if (node.CacheMode is BitmapCache cache)
@@ -732,11 +731,10 @@ private void UpdateNodeViewCacheScale()
                 }
                 else
                 {
-                    if (sharedCache == null)
-                    {
-                        sharedCache = new BitmapCache(currentRenderScale);
-                    }
-                    node.CacheMode = sharedCache;
+                    // Create a unique BitmapCache for each node to ensure thread-safety and reentrancy.
+                    // Sharing a single cache instance across multiple nodes causes race conditions in WPF's
+                    // rendering thread, leading to pure virtual function calls during concurrent access.
+                    node.CacheMode = new BitmapCache(currentRenderScale);
                 }
             }
         }