Description

When adding a Classic block in an empty post, the editor crashes.

Step-by-step reproduction instructions

1. Create a new post
2. Open the sidebar
3. Add a Classic block through the slash inserter

Screenshots, screen recording, code snippet

Environment info

• WordPress 6.0, or WordPress < 6.0 + Gutenberg version >= 13.0
• Firefox & Chrome

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