[controlled-lists] Reference select widget assumes items have URIs

[jacobtylerwalls]

Noticed today while showing archesproject/arches#10569 that the reference select widget ignores items without URIs. Suggest loosening this since we've currently modeled URIs as optional.

https://github.com/archesproject/arches/blob/0552f70c120ddfce3e5e785819a4ac47f2603c21/arches/app/media/js/viewmodels/reference-select.js#L111-L115

[jacobtylerwalls]

@robgaston should we go ahead and make URIs optional for widget display, or should we hold off in case we decide to generate URIs on the fly?

[robgaston]

@jacobtylerwalls I'm sort of thinking that they should remain "optional" for entry, but when they are not provided we should use a default which would just be the PUBLIC_SERVER_ADDRESS concatentated w/ the url to the list item itself. Perhaps it's best if newly created list items are automatically assigned this default entry and URIs are actually required on the model itself (thus we know they are always available on each record)