Cannot convert undefined or null to object #437

Hi there,

I am using this '@tryghost/html-to-mobiledoc' plugin in React APP for converting HTML to mobiledoc, it is a great tool, and its working fine in development mode
but
in production mode (react build) it creates the error 'Cannot convert undefined or null to object' .

Technical details:

"react": "^17.0.2",
"@tryghost/html-to-mobiledoc": "^1.8.6",