Description

Image Lightbox (expand on click) in Gutenberg 16.7.0 RC1 works as expected with Theme Twenty Twenty-Two

After changing to classic Theme Twenty Sixteen (or GeneratePress) an error occurs:
Warning: Array to string conversion in ...\wp-includes\formatting.php on line 1104

Checked:

Visual bug:

1. Image looks regular
2. on mouseover: image disappears and is replaced with a monochrome coloured area of same size
3. click on image opens lightbox as expected
4. click again closes lightbox as expected
5. image was again replaced with coloured area (even without mouseover!)
6. clicking elsewhere make image reappear like regular

Step-by-step reproduction instructions

1. Install Gutenberg 16.7.0 RC1
2. change to theme Twenty Sixteen
3. add page/post
4. add image
5. activate "expand on click"
6. view page
7. try lightbox-efect

Screenshots, screen recording, code snippet

No response

Environment info

WP 6.3.1
Gutenberg 16.7.0 RC1
Themes: Twenty Sixteen, GeneratePress

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