Fatal error on front end: Call to undefined method WP_Theme_JSON::get_custom_css()

[iandunn]

Description

Call to undefined method WP_Theme_JSON::get_custom_css() in wp-content/plugins/gutenberg/lib/compat/wordpress-6.2/get-global-styles-and-settings.php:84

gutenberg/lib/compat/wordpress-6.2/get-global-styles-and-settings.php

Line 84 in 0b8f0d9

$stylesheet = $tree->get_custom_css();

That doesn't exist in https://github.com/WordPress/gutenberg/blob/0b8f0d9c3201dc502d22c3bf8ab478ce7722755d/lib/class-wp-theme-json-resolver-gutenberg.php

Step-by-step reproduction instructions

1. Install WP 6.1 branch from https://core.svn.wordpress.org/branches/6.1 @ r55024 (the latest as of this report)
2. Install Gutenberg 15.3.0 from the plugin repo
3. Activate TwentyTwentyTwo
4. Visit the front end

Screenshots, screen recording, code snippet

No response

Environment info

No response

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes

[t-hamano]

Thanks for the report.
I think this issue has been fixed in #48648 and backported to Gutenberg 15.3.1. The same problem was reported in Slack.