Checkmk Werk 12527: Fix error handling of missing dashlet types

ID: 12527 Title: Fix error handling of missing dashlet types Component: Multisite Level: 1 Class: Bug fix Version: 2.1.0i1 If a dashboard contained a dashlet type that is not known, a KeyError occurred. Now a static dashlet is rendered instead, showing a message to remove the unknown dashlet type from the dashboard configuration.