Fix invalid BT node decorator linkage after removing it

#2059

Source/Editor/Surface/Archetypes/BehaviorTree.cs

@@ -755,6 +755,29 @@ namespace FlaxEditor.Surface.Archetypes
                 }
             }
 
+            /// <inheritdoc />
+            public override void OnDeleted(SurfaceNodeActions action)
+            {
+                // Unlink from the current parent (when deleted by user)
+                var node = Node;
+                if (node != null)
+                {
+                    if (action == SurfaceNodeActions.User)
+                    {
+                        var decorators = node.DecoratorIds;
+                        decorators.Remove(ID);
+                        node.DecoratorIds = decorators;
+                    }
+                    else
+                    {
+                        node._decorators = null;
+                        node.ResizeAuto();
+                    }
+                }
+
+                base.OnDeleted(action);
+            }
+
             public override void OnSurfaceCanEditChanged(bool canEdit)
             {
                 base.OnSurfaceCanEditChanged(canEdit);

Source/Editor/Surface/Undo/AddRemoveNodeAction.cs

@@ -19,6 +19,7 @@ namespace FlaxEditor.Surface.Undo
         private ushort _typeId;
         private Float2 _nodeLocation;
         private object[] _nodeValues;
+        private SurfaceNodeActions _actionType = SurfaceNodeActions.User; // Action usage flow is first to apply user effect such as removing/adding node, then we use Undo type so node can react to this
 
         public AddRemoveNodeAction(SurfaceNode node, bool isAdd)
         {
@@ -38,6 +39,7 @@ namespace FlaxEditor.Surface.Undo
                 Add();
             else
                 Remove();
+            _actionType = SurfaceNodeActions.Undo;
         }
 
         /// <inheritdoc />
@@ -67,8 +69,8 @@ namespace FlaxEditor.Surface.Undo
             else if (_nodeValues != null && _nodeValues.Length != 0)
                 throw new InvalidOperationException("Invalid node values.");
             node.Location = _nodeLocation;
-            context.OnControlLoaded(node, SurfaceNodeActions.Undo);
-            node.OnSurfaceLoaded(SurfaceNodeActions.Undo);
+            context.OnControlLoaded(node, _actionType);
+            node.OnSurfaceLoaded(_actionType);
 
             context.MarkAsModified();
         }
@@ -89,7 +91,7 @@ namespace FlaxEditor.Surface.Undo
 
             // Remove node
             context.Nodes.Remove(node);
-            context.OnControlDeleted(node, SurfaceNodeActions.Undo);
+            context.OnControlDeleted(node, _actionType);
 
             context.MarkAsModified();
         }

Source/Editor/Surface/VisjectSurface.cs

@@ -837,7 +837,7 @@ namespace FlaxEditor.Surface
                         actions.Add(action);
                     }
 
-                    Undo.AddAction(new MultiUndoAction(actions, nodes.Count == 1 ? "Remove node" : "Remove nodes"));
+                    AddBatchedUndoAction(new MultiUndoAction(actions, nodes.Count == 1 ? "Remove node" : "Remove nodes"));
                 }
             }