Demos Trailers are nice for some movies, but not all !

When "Demos Trailers" option is activated, EVERY movie start with a random demo trailer.
I'd like an option to play "Demos Trailers" for only movies where a demo trailer is set-up by user.
Or an option to set default demo trailer to "none".

My database is pretty huge and I don't want to edit all my movies to define personnalized demo trailer with nothing selected into !