Cannot export content from LIF where language is None

[pbauer]

Exporting a site with content in the LIF ("en/assets") like classic.demo.plone.org fails with:

  File "/Users/pbauer/workspace/demo.plone.org/classic/./bin/export-distribution", line 10, in <module>
    sys.exit(export())
             ^^^^^^^^
  File "/Users/pbauer/workspace/demo.plone.org/classic/lib/python3.12/site-packages/plone/distribution/cli/__init__.py", line 49, in export
    results = get_exporter(site).export_site(path, options=namespace)
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/pbauer/workspace/demo.plone.org/classic/lib/python3.12/site-packages/plone/exportimport/exporters/__init__.py", line 72, in export_site
    new_paths = exporter.export_data(path, options=options)
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/pbauer/workspace/demo.plone.org/classic/lib/python3.12/site-packages/plone/exportimport/exporters/content.py", line 163, in export_data
    return super().export_data(base_path, data_hooks, obj_hooks, options=options)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/pbauer/workspace/demo.plone.org/classic/lib/python3.12/site-packages/plone/exportimport/exporters/base.py", line 77, in export_data
    paths = self.dump()
            ^^^^^^^^^^^
  File "/Users/pbauer/workspace/demo.plone.org/classic/lib/python3.12/site-packages/plone/exportimport/exporters/content.py", line 138, in dump
    path = self.dump_one(obj)
           ^^^^^^^^^^^^^^^^^^
  File "/Users/pbauer/workspace/demo.plone.org/classic/lib/python3.12/site-packages/plone/exportimport/exporters/content.py", line 119, in dump_one
    data = self.serialize(obj)
           ^^^^^^^^^^^^^^^^^^^
  File "/Users/pbauer/workspace/demo.plone.org/classic/lib/python3.12/site-packages/plone/exportimport/exporters/content.py", line 89, in serialize
    data = fixer.func(data, obj, config)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/pbauer/workspace/demo.plone.org/classic/lib/python3.12/site-packages/plone/exportimport/utils/content/export_helpers.py", line 133, in fix_language
    token = item.get("language", {}).get("token", placeholder)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'get'

So "language": null, needs to be ok during export. Fixing a missing language is a task that the import (not the export) should handle (depending on the language of the parent).