Changes to Get the network fees

the response property _status/messages/items/data became nullable for the status 400

the response property _status/messages/items/data became nullable for the status 404

the response property _status/messages/items/data became nullable for the status 500

the response property _status/messages/items/detail became nullable for the status 400

the response property _status/messages/items/detail became nullable for the status 404

the response property _status/messages/items/detail became nullable for the status 500