issue with mkdocs-static-i18n

[yaroslav-khomyak]

I'm using mkdocs-static-i18n for multilingual docs.

When I put literate-nav before i18n - I get warning, and nav is messed up:

literate-nav plugin created the nav based on files that were subsequently modified by another MkDocs plugin! Re-order plugins in mkdocs.yml so that literate-nav appears later.

When I put literate-nav last - I get errors and server is not started at all:

INFO     -  Building en documentation
Traceback (most recent call last):
  File "C:\Program Files\WindowsApps\PythonSoftwareFoundation.Python.3.9_3.9.1776.0_x64__qbz5n2kfra8p0\lib\runpy.py", line 197, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "C:\Program Files\WindowsApps\PythonSoftwareFoundation.Python.3.9_3.9.1776.0_x64__qbz5n2kfra8p0\lib\runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "C:\Users\jhm\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\Scripts\mkdocs.exe\__main__.py", line 7, in <module>
  File "C:\Users\jhm\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\click\core.py", line 1137, in __call__
    return self.main(*args, **kwargs)
  File "C:\Users\jhm\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\click\core.py", line 1062, in main
    rv = self.invoke(ctx)
  File "C:\Users\jhm\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\click\core.py", line 1668, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "C:\Users\jhm\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\click\core.py", line 1404, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "C:\Users\jhm\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\click\core.py", line 763, in invoke
    return __callback(*args, **kwargs)
  File "C:\Users\jhm\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\mkdocs\__main__.py", line 173, in serve_command
    serve.serve(dev_addr=dev_addr, livereload=livereload, **kwargs)
  File "C:\Users\jhm\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\mkdocs\commands\serve.py", line 54, in serve
    config = builder()
  File "C:\Users\jhm\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\mkdocs\commands\serve.py", line 49, in builder
    build(config, live_server=live_server, dirty=dirty)
  File "C:\Users\jhm\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\mkdocs\commands\build.py", line 309, in build
    config['plugins'].run_event('post_build', config=config)
  File "C:\Users\jhm\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\mkdocs\plugins.py", line 96, in run_event
    result = method(**kwargs)
  File "C:\Users\jhm\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\mkdocs_static_i18n\plugin.py", line 551, in on_post_build
    nav = config["plugins"].run_event("nav", nav, config=config, files=files)
  File "C:\Users\jhm\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\mkdocs\plugins.py", line 94, in run_event
    result = method(item, **kwargs)
  File "C:\Users\jhm\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages\mkdocs_literate_nav\plugin.py", line 46, in on_nav
    if files != self._files:
AttributeError: 'LiterateNavPlugin' object has no attribute '_files'