No Matching Data not handled correctly in query_unavailability_transmission(): throws error 'Bad Zip File: file is not a zip file'

In case the API returns No Matching Data (Reason/code 999), the response is an Acknowledgement_MarketDocument  xml with the error, not a zip. parse_unavailabilities() however assumes a zip file is returned and tries to process that. The result is the error 'Bad Zip File: file is not a zip file'. 
