Cannot set up editor with custom blocks only

[polysiya]

Describe the bug I cannot run editor when setting up with custom blocks only. It seems essential to use the 'paragraph' default block.

To Reproduce codesandbox: https://codesandbox.io/s/red-sun-hpfypf

Misc

• Node version: v18.15.0
• Package manager: npm
• Browser: chrome latest version