Describe the bug
Introduced in #17151. Quoting from https://github.com/WordPress/gutenberg/pull/17151#issuecomment-591633757
The introduction of gutenberg_extend_settings_image_dimensions breaks Gutenberg in WordPress 5.2.x, due to the call to wp_get_registered_image_subsizes, a function introduced in 5.3.0.
The Gutenberg plugin requires WordPress 5.2.0+. We should either bump that to 5.3.0, or guard against missing wp_get_registered_image_subsizes in lib/client-assets.php.
If there's no easy alternative and since WP 5.4 is very close, we can consider updating the minimum version required by the Gutenberg plugin to 5.3.
Yes to me it seems we should update the minimum version on the plugin.
Follow-up PR: #20628
Most helpful comment
If there's no easy alternative and since WP 5.4 is very close, we can consider updating the minimum version required by the Gutenberg plugin to 5.3.