Unable to download custom blobs by clicking on filename

Not able to download a custom blob by clicking on the filename because the URL shows as /nuxeo/ui/undefined. This is because the downloadUrl and viewUrl is not defined on custom blob properties but only on the hardcoded properties

• file:content
• files:files
• picture:views
• vid:storyboard
• vid:transcodedVideos

Steps to reproduce:

1. Deploy the attached Studio project to your local instance
2. Create a document of type 'TestFile' and add at least one document to the Test Attachments section in the create layout
3. In the metadata panel you will see the attachment you added
4. Hover over the filename
5. Click on the filename to download the blob

Actual Results: Hovering over the filename ends in /nuxeo/ui/undefined. Clicking on the filename does not download the blob. Instead it takes you to an error page

Expected Results: Clicking on the filename downloads the blob