@gopher.ny I was just in the process of creating a Room Lighting App.
I'd just entered the "Name" then the "Command with Activator Device" name. Then, I was in the "Means to Activate Lights" (I'd selected a button) then clicked on "Activate Light Options" when it blew up with:
I had not yet selected ANY devices. It seems that trying to set this option with no devices set yet creates that error (it did it again--but stopped when I added 1 device).