WooCommerce 8.9.1: Dot release

Fixing warnings when loading guest sessions in the Cart and Checkout Blocks

Skip serialization for customer meta and be more defensive around loading it (#47514)

This PR addresses issue #47485, which caused the warning Warning: foreach() argument must be of type array|object, string given when a guest session was loaded after upgrading to 8.9. This PR skips the serialization for customer metadata and enhance the robustness of its loading mechanism, which is crucial to prevent stores from displaying warnings upon the first load due to outdated guest sessions.

Prevent duplicate auto-installation of Legacy REST API

If the Legacy REST API plugin is auto-installed once, do not auto-install a second time. (#47563)

The current behavior automatically reinstalls the Legacy REST API plugin during updates if it detects the plugin is enabled, potentially leading to unnecessary installations if the plugin is manually removed. To address this, changes have been made to ensure the automatic installation occurs only once, eliminating the need for manual intervention to reinstall or remove the plugin on subsequent updates.

Prevent unnecessary calls for stores without Woo Marketplace products

Prevent calling wccom when the payload is empty for update check (#47507)

Currently, stores that do not have any Woo Marketplace plugins will still make unnecessary calls to the update-check endpoint, and subsequently will receive a 400 (because the endpoint expects at least one product in the API payload). This mechanism is not needed for such a store. Although there is no direct impact on stores because we already handle HTTP error cases, this PR is intended to save on resources wasted by unnecessary calls.

Fix modal crashing behavior in the Product Editor

Product Editor: Fix modal block editor crashing when Add button clicked with Gutenberg 18.3.0 (#47561)

This PR fixes the modal block editor crashing when clicking the + (Add) button in the modal block editor header to bring up the block inserter sidebar when Gutenberg 18.3.0 is installed.

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