Headings broken with Gutenberg 6.8.0

[fbertram]

Description: After upgrading to Gutenberg 6.8.0, all heading blocks return the message "This block has encountered an error and cannot be previewed.".

How to reproduce:

1. fresh install of WordPress v5.2.4 (I am using a Docker-based install on localhost)
2. remove all plugins (Akismet, Dolly)
3. install and activate Neve theme v2.4.3
4. remove all other themes (2016 - 2019)
5. edit 'Privacy Policy' page => everything seems to be ok
6. install and activate Gutenberg plugin v6.8.0
7. edit 'Privacy Policy' page => Heading blocks no longer show but display 'This block has encountered an error and cannot be previewed.' Please note that the page renders fine, even with the blocks displaying errors.
8. downgrade Gutenberg plugin to v6.7.0
9. edit 'Privacy Policy' page => everything works fine again.

Expected behaviour:

With Gutenberg 6.8.0, headings should be editable, and not display an error message.

Current behaviour:

Headings cannot be edited, show error message "This block has encountered an error [...]"

Reference:

This might be linked to the following issue w/ Gutenberg: WordPress/gutenberg#18232

Technical info

• WordPress version: x5.2.4
• Gutenberg 6.8.0
• Theme version: Neve 2.4.3

[fbertram]

it seems the issue can be solved with a minor edit: in Neve's inc/core/front_end.php:

change: add_theme_support( 'editor-color-palette', $this->get_gutenberg_color_palette() );
to: add_theme_support( 'editor-color-palette', array() );

Not sure which side-effects this might have.

[selul]

@fbertram thanks for reporting.

We will look into this !

[alcarazzam]

Confirmed with the same versions of @fbertram and a child theme of Neve.

[selul]

@fbertram @m-alzam we have found the glitch, the next version will include the fix.