Checkmk Werk 12374: API time_period: fixing show endpoint which failed when time period with no exclude was called

ID: 12374 Title: API time_period: fixing show endpoint which failed when time period with no exclude was called Component: Core & setup Level: 1 Class: Bug fix Version: 2.1.0i1 In the previous version, the show endpoint of the time period failed when a time period had no exclude configured. This werk fixes this behaviour.