Fix visject connections redo

Previously, it would create double connections

Source/Editor/Surface/Undo/BoxHandle.cs

@@ -10,7 +10,7 @@ namespace FlaxEditor.Surface.Undo
     /// The helper structure for Surface node box handle.
     /// </summary>
     [HideInEditor]
-    public struct BoxHandle
+    public struct BoxHandle : IEquatable<BoxHandle>
     {
         private readonly uint _nodeId;
         private readonly int _boxId;
@@ -51,5 +51,27 @@ namespace FlaxEditor.Surface.Undo
                 throw new Exception("Missing box.");
             return box;
         }
+
+        /// <inheritdoc />
+        public override bool Equals(object obj)
+        {
+            return obj is BoxHandle handle && Equals(handle);
+        }
+
+        /// <inheritdoc />
+        public bool Equals(BoxHandle other)
+        {
+            return _nodeId == other._nodeId &&
+                   _boxId == other._boxId;
+        }
+
+        /// <inheritdoc />
+        public override int GetHashCode()
+        {
+            unchecked
+            {
+                return (_nodeId.GetHashCode() * 397) ^ _boxId.GetHashCode();
+            }
+        }
     }
 }

Source/Editor/Surface/Undo/ConnectBoxesAction.cs

@@ -104,9 +104,12 @@ namespace FlaxEditor.Surface.Undo
             }
             for (int i = 0; i < output.Length; i++)
             {
-                var box = output[i].Get(context);
-                oB.Connections.Add(box);
-                box.Connections.Add(oB);
+                if (!output[i].Equals(_input))
+                {
+                    var box = output[i].Get(context);
+                    oB.Connections.Add(box);
+                    box.Connections.Add(oB);
+                }
             }
 
             toUpdate.AddRange(iB.Connections);