What are the steps to reproduce your problem?

When the loading of reports takes a while, then during configuration of a report following can happen:

Create Process Report
Select Process
Select any view
Select any group by
(Select any Visualization)
Notice that report is still loading:
Click on button for configuration popover
Error: Cannot read property 'type' of undefined

Hint: It is hard to reproduce it if the response from backend (evaluation) comes back quickly.

What is the problem?
FrontEnd shows
Error: Cannot read property 'type' of undefined
Afterwards its broken. You need to reload the page.

What would be the expected behavior:
No error. Either config button stays disabled during loading or empty popover.
I guess disabled would be good.

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