Checkmk Werk 12139: Backup schedule: Fix empty "time of day" selection

ID: 12139 Title: Backup schedule: Fix empty "time of day" selection Component: Setup Level: 1 Class: Bug fix Version: 2.1.0i1 The "time of day" field could previously be saved with an empty field. This resulted to an exception (TypeError (cannot unpack non-iterable NoneType object)) on the resulting page. The previously saved configs can now be read.