Default priority menu differs on config screen and in code

Sorry if the title's a bit unclear. Currently if you visit the admin screen, it's not possible to select None as an option for priority menu (and it defaults to Primary links). However, in the code, if no variable's set it doesn't default to that, it just immediately reads from the DB. (This just caused me a problem where everything looked ok on the menutrails admin screen, but the breadcrumbs sometimes came from the wrong menu.)

I guess a fix would be to either modify the code to default to primary links, or to include a None option in the admin screen. I'd happily supply a patch if you indicated which you'd prefer (I'd go for the latter).

Thanks for a v. important module!

Andy