change default MLD value in otuput csv to None

        for testcase in testcases:

            fulltestname = testcase.get('file') + "::" + testcase.get('name')

            system_out = testcase.find(".//system-out")

            mld_val = 0

            mld_val = None

            if system_out is not None:

                for line in system_out.text.split('\n'):

                    if line.startswith('MLD:'):