Ability to create work without attaching a fileset

[dolsysmith]

This is possible in GWSS 2.x when creating a work in the UI. It is possible in Hyrax 5 with Bulkrax, though it is not possible currently in the UI. Are there good reason for that?

[alepbloyd]

I had this required when we were using iiif_print for derivatives - I forget the precise reason but something was not working with empty filesets, so I configured the application to require filesets. Now that we aren't using iiif_print, I think we could turn that off. The setting is in config/initializers/hyrax.rb, under config.work_requires_files = true