Description

The gutenberg_render_block_core_post_terms function is supposed to return string and other code is expecting a string. However, the function directly returns the output of the get_the_term_list which may return string|false|WP_Error.

When a WP_Error is returned, there is a fatal error emitted in WordPress core's WP_Block::render where the output is typecasted to string:

Uncaught Error: Object of class WP_Error could not be converted to string 

IMHO, the code of the gutenberg_render_block_core_post_terms should check the output value of the get_the_term_list and eventually change the output similarly how WordPress core handles the WP_Error situations when dealing with the function.

Step-by-step reproduction instructions

1. Have a block rendered by the gutenberg_render_block_core_post_terms on a page.
2. Make the get_the_term_list to return an instance of WP_Error (eg.: by filtering the get_the_terms)
3. Load the page

Screenshots, screen recording, code snippet

No response

Environment info

WordPress 6.7 alpha, Gutenberg 19.2.0, PHP 8.1

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