Using the widget Files triggers an error

1. install Nuxeo
2. install JSF UI
3. In Studio, create a custom document type having a field with files:files (see dragAndDrogFilesWidget.png)
4. sync the project with the server
5. create a document and attach 3 documents using the button Add New Attached File
6. save the document
7. observe the server logs contain:

   2018-09-19 16:26:32,100 ERROR [http-nio-0.0.0.0-8080-exec-7] [org.nuxeo.ecm.core.api.model.impl.RemovedProperty] Property 'files/-1/filename' is marked as removed from 'files' schema, don't use it anymore. Return null
   2018-09-19 16:26:32,100 ERROR [http-nio-0.0.0.0-8080-exec-7] [org.nuxeo.ecm.core.api.model.impl.RemovedProperty] Property 'files/-1/filename' is marked as removed from 'files' schema, don't use it anymore. Do nothing
   

Expected behavior: there should not be any error and filename property should not be used
Note: After further testing, it seems the issue comes from Studio generating this code (see OSGI-ING/extensions.xml file inside the attached ffischer-9-ffischer.zip file, see NXS-5019 for this:

      <widget name="files" type="filesList">
        <labels>
          <label mode="any">Files</label>
        </labels>
        <translated>false</translated>
        <fields>
          <field>files:files</field>
        </fields>
        <subWidgets>
          <widget name="sub0" type="file">
            <labels>
              <label mode="any"></label>
            </labels>
            <translated>false</translated>
            <fields>
              <field>file</field>
              <field>filename</field>
            </fields>
          </widget>
        </subWidgets>
      </widget>