Is this a regression?
Rather than a regression, it seems as if it has been always there... I have just tried this in another computer with nightly SVN 11628 (from April 2019), and the same thing happens. I can't prevent any chosen folder from being deleted.
If needed, I will create a ticket for this later.
As for the steps to reproduce, it's quite easy:
- create a new empty project
- in project properties, set the project type to Commands only
- in Objects output dir, type or choose any folder and press OK
- whenever you reenter project properties, the 'Objects output dir' field has been deleted