Once the SEO feature is enabled and configured for a content type it cannot be loaded anymore via REST API. A HTTP 500 is returned.

Steps to reproduce

1. Enable SEO for Content Type
2. Configure seo field mappings
3. Save CT changes
4. Load content type via REST
   /api/ibexa/v2/content/types/<id>
   application/vnd.ibexa.api.ContentType+json

"errorMessage": "Internal Server Error",
"errorDescription": "Invalid type in Field value hash: object",
"trace": "#0 vendor/ibexa/rest/src/lib/Output/Generator/Json/FieldTypeHashGenerator.php(106):