#31 API POST Intervention

* adds check for deserializing of konova codes

api/utils/serializer/v1/serializer.py

@@ -63,6 +63,8 @@ class AbstractModelAPISerializerV1(AbstractModelAPISerializer):
         Returns:
 
         """
+        if json_str is None or len(json_str) == 0:
+            return None
         code = KonovaCode.objects.get(
             atom_id=json_str,
             code_lists__in=[code_list_identifier]