Favorites API POST no longer works when Folder Creator is removed

When favoriting a Folder via the REST API, if the Folder Creator has been removed from the system, Favorites, in the folder owned by the deleted user no longer register in Share when the API is used.  

Steps to Reproduce:

1. Create users "favuser" and "favuser2"
2. Register user to a site as a "Collaborator"
3. Login using the "favuser" login
4. Create  a folder in the site Document Library
5. Logout of the "favuser" account and log in as "admin"
6. Using the following RestAPI Post call, add a favorite tag to the newly created folder.  

   POST http://localhost:8080/alfresco/api/-default-/public/alfresco/versions/1/people/admin/favorites
   
   {
   "target":{
   "folder":{
   "guid":"9f2afea2-d47c-4000-a9f1-4b29667b689b"
   }
   }
   }
   

7. Check in Share and note that the Favorite star is active
8. Delete the "favtest" user.  
9. Remove the favorites tag via the UI (Click on Star to deselect)
10. Reissue the Favorites RestAPI Post call.

Expected Result:

API returns 201 with Admin as the owner.

Actual Result:

The Favorites icon is not updated.  API sent registers "favtest" as the owner and the REST call appears to work (No error is generated)  Return string contains "createdByUser" "favtest"  The return code is 201 "Successful" even though the favorite Icon is not triggered.