fix notify changes after render() without edit if document undefined

jsonform/gadget_json_generated_form_child.js

@@ -806,6 +806,7 @@
       type = json_field.type[0];
     }
     if (["object", "array"].indexOf(type) >= 0 &&
+        !(path !== "" && default_value === undefined) &&
         getDocumentType(default_value) !== type) {
       if (gadget.props.saveOrigValue) {
         // XXX is not useful for user