fix splay tree

com.unity.uiwidgets/Runtime/codegen/TileContainerRenderObjectMixin.mixin.gen.cs

     {
         D.assert(() =>
         {
-            if (child is ChildType)
+            if (!(child is ChildType))
             {
                 throw new UIWidgetsError(
                     "A $runtimeType expected a child of type $ChildType but received a " +
                 throw new ArgumentException($"index {index}");
             }
 
-            _removeChild(_childRenderObjects[index]);
+            _removeChild(_childRenderObjects.getOrDefault(index, null));
             adoptChild(value);
             _childRenderObjects[index] = value;
         }
 
     public override void attach(object owner)
     {
-     //   base.attach(owner);
+        base.attach(owner);
-       // base.detach();
+        base.detach();
         _childRenderObjects.Values.ToList().ForEach((child) => child.detach());
     }
 

com.unity.uiwidgets/Runtime/codegen/TileContainerRenderObjectMixin.mixin.njk

     SplayTree<int, ChildType> _childRenderObjects = new SplayTree<int, ChildType>();
 
     /// The number of children.
-    private int childCount
+    protected int childCount
-    ICollection<ChildType> children
+    protected ICollection<ChildType> children
-    ICollection<int> indices
+    protected ICollection<int> indices
     {
         get => _childRenderObjects.Keys;
     }
     {
         D.assert(() =>
         {
-            if (child is ChildType)
+            if (!(child is ChildType))
             {
                 throw new UIWidgetsError(
                     "A $runtimeType expected a child of type $ChildType but received a " +
                 throw new ArgumentException($"index {index}");
             }
 
-            _removeChild(_childRenderObjects[index]);
+            _removeChild(_childRenderObjects.getOrDefault(index, null));
             adoptChild(value);
             _childRenderObjects[index] = value;
         }
 
     public override void attach(object owner)
     {
-     //   base.attach(owner);
+        base.attach(owner);
-       // base.detach();
+        base.detach();
         _childRenderObjects.Values.ToList().ForEach((child) => child.detach());
     }
 

com.unity.uiwidgets/Runtime/external/SplayTree.cs

             if (key == null) throw new Exception("should input null");
             if (root == null) throw new Exception("root is null");
             int comp = Splay(key);
-            if (comp < 0) return root.Key;
+            if (comp > 0) return root.Key;
             SplayTreeNode node = root.LeftChild;
             if (node == null) throw new Exception("does not exist");
             while (node.RightChild != null) {
             if (key == null) throw new Exception("should input null");
             if (root == null) throw new Exception("root is null");
             int comp = Splay(key);
-            if (comp > 0) return root.Key;
+            if (comp < 0) return root.Key;
             SplayTreeNode node = root.LeftChild;
             if (node == null)  throw new Exception("does not exist");
             while (node.LeftChild != null) {