Make cancelling "delete property" cancel the entire operation

com.unity.shadergraph/Editor/Drawing/Views/MaterialGraphView.cs

 
         void DeleteSelectionImplementation(string operationName, GraphView.AskUser askUser)
         {
+            foreach (var selectable in selection)
+            {
+                var field = selectable as BlackboardField;
+                if (field != null && field.userData != null)
+                {
+                    if (EditorUtility.DisplayDialog("Sub Graph Will Change", "If you remove a property and save the sub graph, you might change other graphs that are using this sub graph.\n\nDo you want to continue?", "Yes", "No"))
+                        break;
+                    return;
+                }
+            }
+
-            bool userNotified = false;
+
-                    if (!userNotified)
-                    {
-                        if (EditorUtility.DisplayDialog("Sub Graph Will Change", "If you remove a property and save the sub graph, you might change other graphs that are using this sub graph.\n\nDo you want to continue?", "Yes", "No"))
-                        {
-                            userNotified = true;
-                        }
-                        else
-                        {
-                            return;
-                        }
-                    }
-                    if (userNotified)
-                    {
-                        var property = (IShaderProperty)field.userData;
-                        graph.RemoveShaderProperty(property.guid);
-                    }
+                    var property = (IShaderProperty)field.userData;
+                    graph.RemoveShaderProperty(property.guid);
+            
             selection.Clear();
         }