Set MountainRange area to -1 explicitly if not set

app/management/commands/import.py

@@ -449,6 +449,10 @@ def handle_object_dict(object_dict, model_name, debug=False):
         for i in ['checked']:
             if i in object_dict:
                 object_dict[i] = True if object_dict[i].lower().strip() == 'true' else False
+        # area field can't be empty
+        if 'area' in object_dict:
+            if object_dict['area'] == '':
+                object_dict['area'] = -1
     if model_name == 'Keyword':
         object_dict['keyword'] = object_dict['keyword_id']
         object_dict.pop('keyword_id')