Merge pull request #96 from ImMin5/master

Set network traffic None type iterable error

src/cloudforet/cost_analysis/manager/cost_manager.py

@@ -795,8 +795,8 @@ def _exclude_cost_data_with_options(result: dict, options: dict) -> bool:
     def _set_network_traffic_cost(
             additional_info: dict, result: dict, usage_type: str
     ) -> dict:
-        meter_category = result.get("metercategory", "")
-        meter_name = result.get("metername", "")
+        meter_category = result.get("metercategory", "") or ""
+        meter_name = result.get("metername", "") or ""
         result_additional_info = result.get("additional_info", {}) or {}
         data_transfer_direction = result_additional_info.get("DataTransferDirection")