astro/cli/install-package.ts: whichPm may return null if ran in an empty directory

[nektro]

Changes

• If whichPm is unable to determine the package manager it will return null, not { name: null }.
• This patch allows the null coalescing already added to work.

Testing

before

❯ npx astro init
Need to install the following packages:
astro@4.6.1
Ok to proceed? (y) y
To continue, Astro requires the following dependency to be installed: @astrojs/db.
Cannot read properties of null (reading 'name')
  Stack trace:
    at installPackage (file:///Users/meghandenny/.npm/_npx/aa98e6899c6baff3/node_modules/astro/dist/cli/install-package.js:79:47)
    at async db (file:///Users/meghandenny/.npm/_npx/aa98e6899c6baff3/node_modules/astro/dist/cli/db/index.js:9:21)
    at async cli (file:///Users/meghandenny/.npm/_npx/aa98e6899c6baff3/node_modules/astro/dist/cli/index.js:169:5)

after change made locally

❯ npx astro init
To continue, Astro requires the following dependency to be installed: @astrojs/db.

  Astro will run the following command:
  If you skip this step, you can always run it yourself later

 ╭──────────────────────────╮
 │ npm install @astrojs/db  │
 ╰──────────────────────────╯

✔ Continue? … no
20:50:22 [ERROR] [check] The `@astrojs/db` package is required for this command to work. Please manually install it in your project and try again.

(I manually selected no, it loaded successfully.)

Docs

this should not require a docs change

[changeset-bot]

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Latest commit: f89d5fd

The changes in this PR will be included in the next version bump.

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[jacobdalamb]

Could this be related to #10748 ?

[nektro]

that issue will likely be fixed by zkochan/packages#188