Optional mdk mapping

ckanext/odsh/helpers.py

@@ -475,7 +475,9 @@ def odsh_load_mdk_sample_dataset():
     try:
         with open(sample_data_file_path) as mapping_json:
              MDK_MAPPING = json.loads(mapping_json.read(), object_pairs_hook=OrderedDict)
-             result = [{'key': key, 'value': MDK_MAPPING[key]} for key in MDK_MAPPING]
+             default = [{'value': u'Musterdatensatz wählen..', 'key': u''}]
+             mdk = [{'key': key, 'value': MDK_MAPPING[key]} for key in MDK_MAPPING]
+             result = default+mdk
     except IOError as err:
         log.error(
             'Could not load sample dataset mapping file from {}'