widget 'multiple document suggestion' should save an empty value when used in a list of strings in a list of complex fields

How to reproduce:

• In Studio
  • create a new document type whose contains a list of complex fields containing a field of type multi-valued of String
  • in the Edition layout and view layout, use widget multiple document suggestion for the metadata of type multi-valued of String
• In a Nuxeo instance
  • Create a document with the type defined above
  • select a document for the metadata of type multi-valued of String and save the document
  • Edit the document, remove the selected document for the metadata of type multi-valued of String and save the document

The metadata of type multi-valued of String is not empty, it still contains document selected before the edition.