Use a more reliable way to convert to string

[bor0]

Description

Due to the recent MFA changes, my role was demoted to Member instead of Admin. When I tried to run vip @97.production config envvar get-all, the variables had the value of null, which caused the following error:

$ vip @97.production config envvar get-all
✕ Please contact VIP Support with the following information:
TypeError: Cannot read properties of null (reading 'toString')
    at /Users/bor0/.nvm/versions/node/v18.11.0/lib/node_modules/@automattic/vip/dist/lib/cli/format.js:75:50
    at Array.map (<anonymous>)
    at /Users/bor0/.nvm/versions/node/v18.11.0/lib/node_modules/@automattic/vip/dist/lib/cli/format.js:75:24
    at Array.forEach (<anonymous>)
    at table (/Users/bor0/.nvm/versions/node/v18.11.0/lib/node_modules/@automattic/vip/dist/lib/cli/format.js:74:8)
    at formatData (/Users/bor0/.nvm/versions/node/v18.11.0/lib/node_modules/@automattic/vip/dist/lib/cli/format.js:37:14)
    at getAllEnvVarsCommand (/Users/bor0/.nvm/versions/node/v18.11.0/lib/node_modules/@automattic/vip/dist/bin/vip-config-envvar-get-all.js:86:38)
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
    at async _args.default.argv (/Users/bor0/.nvm/versions/node/v18.11.0/lib/node_modules/@automattic/vip/dist/lib/cli/command.js:461:11)
Error:  Unexpected error
Debug:  VIP-CLI v3.8.4, Node v18.11.0, darwin 24.0.0 arm64

Ideally, it should have returned something like this instead:

┌──────────────────────┬───────┐
│ name                 │ value │
├──────────────────────┼───────┤
│ AWS_S3_KEY_ADDONS    │ null  │
├──────────────────────┼───────┤
│ AWS_S3_SECRET_ADDONS │ null  │
...

This PR achieves that.

Pull request checklist

• Update SETUP.md with any new environmental variables.
• Update the documentation.
• Manually test the relevant changes.
• Follow the pull request checklist
• Add/update automated tests as needed.

New release checklist

• Automated tests pass.
• The Preparing for release checklist is completed.

Steps to Test

1. Check out trunk.
2. Apply this test.patch
3. Run vip @97.production config envvar get-all
   Expected: error should appear
4. Switch to this branch
5. Run vip @97.production config envvar get-all
   Expected: should be rendered properly

[github-actions]

Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

OpenSSF Scorecard

Package	Version	Score	Details

Scanned Manifest Files

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud