Merge branch 'lukas_issue212_bug_mixed-sampling-data-loading' into 'develop'

Resolve "BUG: mixed sampling causing errors on data loading"

See merge request !188

mlair/helpers/join.py

@@ -46,7 +46,7 @@ def download_join(station_name: Union[str, List[str]], stat_var: dict, station_t
 
     # correct stat_var values if data is not aggregated (hourly)
     if sampling == "hourly":
-        [stat_var.update({k: "values"}) for k in stat_var.keys()]
+        stat_var = {key: "values" for key in stat_var.keys()}
 
     # download all variables with given statistic
     data = None