Check _get_cron_array type in upgrade_590 routine

[chrisvanpatten]

When the upgrade_590 DB routine is run on a site without the cron site option, _get_cron_array returns false which causes a TypeError when the return value is run through array_filter.

​https://github.com/WordPress/WordPress/blob/638ef7815ec29318434365ffde1d3cef7437b948/wp-admin/includes/upgrade.php#L2275-L2277

[25-Jan-2022 21:33:45 UTC] PHP Fatal error:  Uncaught TypeError: array_filter(): Argument #1 ($array) must be of type array, bool given in /var/www/html/web/wp/wp-admin/includes/upgrade.php:2273

In particular, I encountered this on a local multisite network with several sites which had been created but not yet used. Running the upgrade routine worked on the sites which had been used (and thus had cron site options) but failed on the others.

Related: #53940

[peterwilsoncc]

Thanks for logging this Chris, I'll look at getting a fix in for the 5.9.1 release.

Trac ticket: [](https://core.trac.wordpress.org/ticket/54906)

[kapilpaul]

Created patch

[peterwilsoncc]

Thanks for the patch @kapilpaul.

The code looks good to me so I've self assigned the ticket and marked it for commit.

[peterwilsoncc]

In 52656:

Upgrade: Prevent warnings upgrading cron array.

An unvisited site may have an undefined cron array, resulting in _get_cron_array() returning the value false. Previously this would trigger warning in upgrade_590() as the function assumed _get_cron_array() would alway return an array.

No database version change is required as the upgrade routine was successful on sites with a cron array during 5.9.0. On sites without a cron array, the error has already been thrown if they are running db version 51917. This fix is only required for new sites or those upgrading that have skipped 5.9.0.

Follow up to [51917].

Props chrisvanpatten, kapilpaul, SergeyBiryukov.
Fixes #54906.
See #53940.

[peterwilsoncc]

Reopening for merging in to the 5.9 branch.

Merged in ​https://github.com/WordPress/wordpress-develop/commit/9e03599af883484d0a2b35cfe118585df32a331d (canonically https://core.trac.wordpress.org/changeset/52656)

[audrasjb]

In the comment, it could be nice to also mention this ticket (#54906).

Otherwise, the logic in this patch looks good to backport. Adding dev-reviewed keyword.

[peterwilsoncc]

In 52662:

Upgrade: Add follow up ticket ID to upgrade_590() comment.

Follow up to [52656].

Props audrasjb.
See #54906.

[peterwilsoncc]

In 52663:

Upgrade: Prevent warnings upgrading cron array.

An unvisited site may have an undefined cron array, resulting in _get_cron_array() returning the value false. Previously this would trigger warning in upgrade_590() as the function assumed _get_cron_array() would alway return an array.

No database version change is required as the upgrade routine was successful on sites with a cron array during 5.9.0. On sites without a cron array, the error has already been thrown if they are running db version 51917. This fix is only required for new sites or those upgrading that have skipped 5.9.0.

Follow up to [51917].

Props chrisvanpatten, kapilpaul, SergeyBiryukov, audrasjb.
Merges [52656] and [52662] to the 5.9 branch.
Fixes #54906.
See #53940.