Fixed. Note that there was a conflict between the cascading prompt and the fix for BI-Server 5538 (always autoselect first element of a combobox), which would cause the attached report to show an error (you need to select a value) when the UI then auto-selects the value for the user.
Auto-selecting values in case of empty list parameters should be under the control of the server. We have a global config option
and a per-parameter setting to allow this sort of thing on the server side. This way, the validating methods can jump in and that auto-selected value can be used by the subsequent parameters in queries and for other validation purposes.
I therefore disabled that particular fix when the parameter-ui communicates with the reporting plugin. When the parameter UI is used for parametrizationg of any other component (analzyer, dashboard, charts, whatever) the fix for BI-Server 5538 is active.