basepath on NextRequest.nextUrl not set consistent when using basePath and i18n

Verify canary release

• I verified that the issue exists in the latest Next.js canary release

Provide environment information

Operating System:
      Platform: win32
      Arch: x64
      Version: Windows 10 Home
    Binaries:
      Node: 18.15.0
      npm: N/A
      Yarn: N/A
      pnpm: N/A
    Relevant packages:
      next: 13.4.3-canary.1
      eslint-config-next: N/A
      react: 18.2.0
      react-dom: 18.2.0
      typescript: 4.9.5

Which area(s) of Next.js are affected? (leave empty if unsure)

App directory (appDir: true), Internationalization (i18n)

Link to the code that reproduces this issue

https://github.com/paulvanbrenk/basepath-bug-nextjs

To Reproduce

Clone repo
Run npm run dev
navigate to http://localhost:3000/home/fr

Notice output in terminal has an empty basePath.

Compare this to the output when navigating to http://localhost:3000/home/en

Describe the Bug

The basePath in NextRequest.nextUrl in the middleware is not set as expected for any locale that's not the default locale.

See the output from the console.log in the repro.

Expected Behavior

The basePath to be set consistent in dependent of the locale used.

Which browser are you using? (if relevant)

n/a

How are you deploying your application? (if relevant)

n/a

Start with the linked reproduction repository, run npm run dev, and inspect the middleware console output while visiting /home/fr and /home/en. Done means NextRequest.nextUrl.basePath is set consistently for the default and non-default locales.