message: add columns for bootstrap_data
diff: @@ -889,8 +889,11 @@ class Superset(BaseSupersetView): # pylint: disable=too-many-public-methods
  except (SupersetException, SQLAlchemyError):
  datasource_data = dummy_datasource_data
  + columns: List[Dict[str, Any]] = []
  if datasource:
  datasource_data["owners"] = datasource.owners_data
  + if isinstance(datasource, Query):
  + columns = datasource.extra.get("columns", [])
  bootstrap_data = {
  "can_add": slice_add_perm,
  @@ -905,6 +908,7 @@ class Superset(BaseSupersetView): # pylint: disable=too-many-public-methods
  "user": bootstrap_user_data(g.user, include_perms=True),
  "forced_height": request.args.get("height"),
  "common": common_bootstrap_payload(),
  + "columns": columns,
  }
  if slc:
  title = slc.slice_name
  