I am using a quick field to input the name of my camera. I put the following in my Folder Arrangement and Names. And it worked as I wanted.
Then I thought I would try to set it up so that if the camera quick field was empty it would just use the number range. So I changed it to the following.
This creates an entry in the Quick Fields entry area with the title "camera,0.-1,_". I can put something in this new field but now I will only get a number range folder created.
It is probably something you never tested for but it would be convenient if it worked.