iiif plugin, metadata is recomnended but not required for a manifest, absence freeze bookreader

[glorieux-f]

Description

With https://github.com/internetarchive/bookreader/blob/master/BookReaderDemo/demo-iiif.html the canonic iiif book example https://iiif.io/api/cookbook/recipe/0009-book-1/manifest.json does not work in bookreader.

iiif presentation 3.0 spec (same for 2)

Evidence / Screenshot (if possible)

Expectation

Bookreader should handle a valid iiif manifest, even without metadata. Maybe a message could be sent in javascript console or in the info window, to encourage the iiif provider to give metadata.

Context

All.

Proposal & Constraints

Fast fix, some testing in the iiif plugin https://github.com/internetarchive/bookreader/blob/a9c279c66b9eb0d394304dd3fa88aaef88bdfaa9/src/plugins/plugin.iiif.js#L38

Stakeholders

???