[Bug report] 由于存在空白 README.md 导致首页空白

[Sciroccogti]

✅ Checklist

• [X] I am using the latest version

🔎 Description

Concise Description

其实不能算bug，但是确实排查了好久，所以登记一下。

之前的主题要求有 README.md，于是我就也在这个主题的 docs 目录下留了一个空白的 README.md，结果怎么试主页都是空白，能正常显示 导航栏 什么的，而且浏览器也没报错。

Steps to reproduce

在 docs 目录放置空白 README 就会覆盖生成的主页，导致主页空白。

📄 Environment info (npx vuepress info)

System:
    OS: Linux 4.15 Ubuntu 18.04.6 LTS (Bionic Beaver)
    CPU: (2) x64 Intel(R) Xeon(R) Platinum 8163 CPU @ 2.50GHz
    Memory: 2.59 GB / 7.79 GB
    Shell: 4.4.20 - /bin/bash
  Binaries:
    Node: 17.9.0 - /usr/local/bin/node
    Yarn: 1.22.15 - /usr/local/bin/yarn
    npm: 8.7.0 - /usr/local/bin/npm
  Utilities:
    Git: 2.17.1 - /usr/bin/git
  Browsers:
    Chrome: Not Found
    Firefox: Not Found
  npmPackages:
    @vuepress/bundler-vite:  2.0.0-beta.48 
    @vuepress/bundler-webpack: Not Found
    @vuepress/cli:  2.0.0-beta.48 
    @vuepress/client:  2.0.0-beta.48 
    @vuepress/core:  2.0.0-beta.48 
    @vuepress/markdown:  2.0.0-beta.48 
    @vuepress/plugin-active-header-links:  2.0.0-beta.48 
    @vuepress/plugin-back-to-top:  2.0.0-beta.48 
    @vuepress/plugin-container:  2.0.0-beta.48 
    @vuepress/plugin-docsearch: Not Found
    @vuepress/plugin-external-link-icon:  2.0.0-beta.48 
    @vuepress/plugin-git:  2.0.0-beta.48 
    @vuepress/plugin-google-analytics:  2.0.0-beta.48 
    @vuepress/plugin-medium-zoom:  2.0.0-beta.48 
    @vuepress/plugin-nprogress:  2.0.0-beta.48 
    @vuepress/plugin-palette:  2.0.0-beta.48 
    @vuepress/plugin-prismjs:  2.0.0-beta.48 
    @vuepress/plugin-pwa:  2.0.0-beta.48 
    @vuepress/plugin-pwa-popup:  2.0.0-beta.48 
    @vuepress/plugin-register-components: Not Found
    @vuepress/plugin-search: Not Found
    @vuepress/plugin-shiki: Not Found
    @vuepress/plugin-theme-data:  2.0.0-beta.48 
    @vuepress/plugin-toc: Not Found
    @vuepress/shared:  2.0.0-beta.48 
    @vuepress/theme-default:  2.0.0-beta.48 
    @vuepress/utils:  2.0.0-beta.48 
    vue:  3.2.37 
    vue-loader: Not Found
    vue-router:  4.1.3 
    vuepress: ^2.0.0-beta.48 => 2.0.0-beta.48 
    vuepress-vite:  2.0.0-beta.48 
    vuepress-webpack: Not Found

🔗 Reproduction link / repo:

No response