Update the node balance when deleting a duplicate in the AVL tree.

sdk/avltree.h

@@ -276,6 +276,7 @@ static void avl_tree_remove(avl_tree_t *tree, avl_node_t *node)
         node->next_equal->left = node->left;
         node->next_equal->right = node->right;
         node->next_equal->prev_equal = NULL;
+        node->next_equal->balance = node->balance;
 
         if (node->parent)
         {