(Jetpack)(PHP8)(GB 17.1.3) Make the check around $google_fonts_data's array more resilient and return early if key or value is not of the right type

[fullofcaffeine]

Proposed changes:

We've found that in some circumstances (which I couldn't pinpoint yet, exactly) when using PHP8 and Gutenberg 17.1.3+, the $google_fonts_data['fontFamilies'] would be null and cause a fatal. The actual changeset in GB that triggers it (when PHP8 is being used) is this WordPress/gutenberg#55240 adds a more resilient guard around it, extending the current one, and return early if the shape is not correct.

See p1701220768492429-slack-CDLH4C1UZ and p1701369236916389-slack-C05Q5HSS013 for more context and info.

Other information:

• Have you written new tests for your changes, if applicable?
• Have you checked the E2E test CI results, and verified that your changes do not break them?
• Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Jetpack product discussion

Does this pull request change what data or activity we track or use?

Testing instructions:

Steps to reproduce are tricky, see p1701220768492429-slack-CDLH4C1UZ for more info. It needs some WPCOM-specific builds that might not be available in this repo.

[github-actions]

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[github-actions]

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• To test on WoA, go to the Plugins menu on a WordPress.com Simple site. Click on the "Upload" button and follow the upgrade flow to be able to upload, install, and activate the Jetpack Beta plugin. Once the plugin is active, go to Jetpack > Jetpack Beta, select your plugin, and enable the make/load-google-fonts-more-resilient branch.

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[kraftbj]

Marking as a blocker since the fix has been deployed on WP.com Simple, so need to land this before next daily to ensure we don't regress.

[fullofcaffeine]

Marking as a blocker since the fix has been deployed on WP.com Simple, so need to land this before next daily to ensure we don't regress.

Corresponding diff: D129881-code

[fullofcaffeine]

@kraftbj Thanks for adding the changelog!

[arthur791004]

Thanks 👍

Clicked approve by mistake