[REQUIRED] Environment info

firebase-tools: 14.4.0
Platform: macOS

[REQUIRED] Test case

Project structure:

frontend/
├── .firebaserc
├── .gitignore
├── apphosting.yaml
├── components.json
├── firebase-debug.log
├── firebase.json
├── next-env.d.ts
├── next.config.ts
├── package-lock.json
├── package.json
├── postcss.config.mjs
├── README.md
├── tsconfig.json
├── .next/
├── node_modules/
└── src/
├── app/
├── components/
└── lib/

[REQUIRED] Steps to reproduce

1.	Ensure the `firebase.json` is configured as follows:

{
  "apphosting": {
    "backendId": "xxx",
    "rootDir": "/",
    "ignore": [
      "node_modules",
      ".git",
      "firebase-debug.log",
      "firebase-debug.*.log",
      "functions"
    ]
  },
  "emulators": {
    "apphosting": {
      "port": 5002,
      "rootDirectory": "./"
    },
    "ui": {
      "enabled": true,
      "port": 8000
    },
    "singleProjectMode": true
  }
}

2.	Run the emulator:

firebase emulators:start

[REQUIRED] Expected behavior

The App Hosting emulator should start successfully with the following output:

i emulators: Starting emulators: apphosting
i apphosting: starting app with: 'npm run dev'

[email protected] dev
next dev --turbopack

⚠ emulators: The Emulator UI is not starting, either because none of the running emulators have a UI component or the Emulator UI cannot determine the Project ID. Pass the --project flag to specify a project.
i apphosting: connecting apphosting emulator

...
✓ Ready in 771ms

[REQUIRED] Actual behavior

The following error occurs when starting the App Hosting emulator:

[debug] [2025-05-17T06:42:28.751Z] TypeError: Cannot convert undefined or null to object
at Function.values ()
at tripFirebasePostinstall (/.../firebase-tools/lib/emulator/apphosting/serve.js:138:41)
at serve (/.../firebase-tools/lib/emulator/apphosting/serve.js:96:15)
...

This issue appears only in version 14.4.0.
Downgrading to version 13.3.1 resolves the issue.