bugfix for renaming of stat_var values

src/join.py

@@ -45,6 +45,7 @@ def download_join(station_name: Union[str, List[str]], stat_var: dict, station_t
     vars_dict = load_series_information(station_name, station_type, network_name, join_url_base, headers)
 
     # correct stat_var values if data is not aggregated (hourly)
+    if sampling == "hourly":
         [stat_var.update({k: "values"}) for k in stat_var.keys()]
 
     # download all variables with given statistic