Fix display of nuxeo-document-suggestion when the stored value corresponds to a non-visible document

This ticket is related to ELEMENTS-860 where nuxeo-document-suggestion had a bug when one of the values stored in a multi-valued metadata was deleted. This bug has been correctly fixed, now the problem is with a single Document metadata.

Steps to reproduce

1. Deploy the attached jar to nxserver/plugins
2. Log in as user JDOE
3. Go to a Workspace or to the JDOE's workspace
4. Create a Document "Suggest Doc" and select 1 document for the "mydoc" field: Templates
5. Log in as Administrator
6. Block permissions for everyone on the Templates document
7. Log in as JDOE
8. Go back to the newly created document
9. Observe that nothing is displayed for the "mydoc" field
10. Edit the document
11. Observe that nothing is displayed in the suggestion field for "mydoc"

Expected behavior:

The nuxeo-document-suggestion element should display the id of the document which are not visible because of lack of permissions.