Too many one-off checks for empty value

[mde]

Check for "not empty string, not null, not undefined" is being done inline in multiple places. Make this all one single function call.

[lgomezma]

Indeed, otherwise it becomes too cumbersome. Where would it be the best place to define such function? I'm still getting used to model's architecture...

[mde]

I went ahead and added it to the utilities library, in the core, since it's general-purpose: mde/utilities@c5fcbb5