Dropdown selector with no options. Disabled or not?

I have a dropdown HTML select menu. Entries will appear once a calculation is performed, however until then, there is nothing available, and therefore the dropdown is empty. The dropdown should be there because it will make clear that the output area is available, but nothing has been calculated.

My concern is about the state of the dropdown. I don't recall any similar situation anywhere, and neither the macOS or the Windows HIG specify what should be done in this case. Should the select be empty, but selectable (eventually showing an empty dropdown menu) or should the control be disabled altogether?