Brief summary of the bug. What is it ? Where is it ?

It may happen that an existing kpi report is changed in a way that actually makes it incompatible for the process overview page. The main cause is that a former single number report is changed in a way that the result is not a single number anymore.

Steps to reproduce:

1. Create a single number report and configure it as KPI report
2. Go to the process overview page, it should be listed there an all be fine
3. open the report and change it's setup, e.g. adding another process and grouping the result by process
4. save it
5. Open the process overview page again

Actual result:

The page fails loading the process overview the API shows this or a similar error related to the internal result casting a list to a double.

See attached screen recording.

Expected result:

Either we need to ensure that once a report becomes not kpi compatible that the flag is properly reset or we should handle this situations gracefully during exaluation, ignoring the result.