Super Cache: Make sure plugin links is an array before using it

[donnchawp]

It was reported that adding the Settings link to the plugins links on the Plugins page caused an error for a user because $links was null. This patch checks to make sure that $links is actually an array before using it.

Fixes #37600

Proposed changes:

• Check that $links is an array

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:

Apply PR
You may need to adjust the path to wp-cache.php in the PR to match how you have WPSC installed. It may be installed in wp-super-cache-dev or super-cache.
Load Plugins page and note the links below the WP Super Cache title.

I can't reproduce this error, but this one line fix should fix it.

[github-actions]

Thank you for your PR!

When contributing to Jetpack, we have a few suggestions that can help us test and review your patch:

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Super Cache plugin:

• Next scheduled release: July 2, 2024.
• Scheduled code freeze: June 24, 2024.

If you have any questions about the release process, please ask in the #jetpack-releases channel on Slack.

[pkuliga]

LGTM 👍