Error when downloading a multivalued blob in a multivalued complex

To reproduce the issue:

1. use the JSF UI
2. create a schema with a multivalued complex having a multivalued blob field
3. use the schema in a doctype and create a layout that displays the complex field
4. deploy the project

Server-side:

1. in the layout, attach a blob on the multivalued field and save
2. click the filename to download it
3. observe the following error:

   java.util.HashMap cannot be cast to org.nuxeo.ecm.core.api.Blob