default children if empty

src/tree.py

@@ -213,6 +213,8 @@ class TreeWalker:
             config = {
                 "node_id": self.gen_node_id(),
                 "keywords": [],
+                "children":[],
+                "export":[]
             }
             dump_json(config_path, config, exist_ok=True, override=True)
         else: