PHP Notice during cron related to Sync

### Impacted plugin

Jetpack

### Quick summary

During WordPress cron, the following PHP Notice is often hit:

**E_NOTICE** Undefined offset: 1
**URL** https://example.orgwp-cron.php?doing_wp_cron=timestamp
**File** wp-content/plugins/jetpack/jetpack_vendor/automattic/jetpack-sync/src/modules/class-posts.php:391

**Stack Trace** do_action_ref_array('grunion_scheduled_delete'), WP_Hook->do_action, WP_Hook->apply_filters, Automattic\Jetpack\Forms\ContactForm\Util::grunion_delete_old_spam, wp_delete_post, delete_metadata_by_mid, do_action('deleted_post_meta'), WP_Hook->do_action, WP_Hook->apply_filters, Automattic\Jetpack\Sync\Listener->action_handler, Automattic\Jetpack\Sync\Listener->enqueue_action, apply_filters('jetpack_sync_before_enqueue_deleted_post_meta'), WP_Hook->apply_filters, Automattic\Jetpack\Sync\Modules\Posts->filter_meta

### Steps to reproduce

Unknown.

### A clear and concise description of what you expected to happen.

_No response_

### What actually happened

_No response_

### Impact

Some (< 50%)

### Available workarounds?

There is no user impact

### Platform (Simple and/or Atomic)

Self-hosted

### Logs or notes

_No response_