Failure of multi-language support

Describe the bug

First of all, my English may not be good, please forgive me. In the test of vitepress@0.13.2 , multilanguage support worked. But when I upgraded vitepress@0.16.1, I put the same directory configuration structure into the framework, and when I started it, the page navigation bar didn't display properly. In debug mode, the parameters associated with the locales cannot be seen. Maybe I did something wrong, but my configuration item is exactly the same as @0.13.2, which is makes me confused, so I would like to ask if the configuration related to multilingual support has changed， and I suggest you check if there is any error.

Reproduction

npm install vitepress. npm run dev. open the page at localhost.

Expected behavior

In VitePress@0.13.2, The navigation bar is displayed correctly

With the same configuration in VitePress@0.16.1, the navigation bar is not displayed, as shown in the following picture.

The personal configuration is shown in the following picture

In debug mode, the locale parameter is null

System Info

System:
    OS: Windows 10 10.0.19042
    CPU: (8) x64 Intel(R) Core(TM) i5-8300H CPU @ 2.30GHz
    Memory: 7.26 GB / 15.85 GB
  Binaries:
    Node: 12.18.3 - C:\Program Files\nodejs\node.EXE
    Yarn: 1.22.10 - ~\AppData\Roaming\npm\yarn.CMD
    npm: 6.14.6 - C:\Program Files\nodejs\npm.CMD
  Browsers:
    Chrome: 92.0.4515.159
    Edge: Spartan (44.19041.1023.0), Chromium (92.0.902.73)
    Internet Explorer: 11.0.19041.906
  npmPackages:
    vitepress: ^0.16.1 => 0.16.1

Additional context

No response

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vuejs / vitepress