Emptied multi-value property stored in database

The database should not store empty multi-value properties. This causes issues with searches.

Replication Steps

1. Create document in Web UI, and add a value for dc:subjects.
2. Edit document and remove the value.
3. Export JSON and see e.g.:

   {
     "path": "/config/UserWorkspaces/Administrator/null-1",
     "properties": {
       "dc:subjects": [
       ],
       "dc:title": "null-1",
     },
     "title": "null-1",
     "type": "File",
     "uid": "169d006e-52bd-4e71-858b-6f397a08a902"
   }
   

4. Export bjson from database (MongoDB here):

   > mongosh
   test> use nuxeo
   nuxeo> db.default.find({'ecm:id': '169d006e-52bd-4e71-858b-6f397a08a902'})
   [
     {
       _id: ObjectId("66d8570bc84cbc6f56e26713"),
       ...
       'dc:subjects': [],
       ...
     }
   ]
   

5. Search for document (using Web UI NXQL Admin Tool, i.e. against db):

   SELECT * FROM File WHERE dc:title = 'null-1' AND dc:subjects IS NULL
   

   •  Expected result:

     Found document: null-1
     

   • Actual result:

     No documents match the search criteria.
     

Issue observed on 2023.7.9 and 2023.10.13

Note:

• This issue arises from a MV property that has had a value set and then removed. It does not affect properties that have never been set.