Conversion fails – because of nullable attributes?

[R3gi]

When I try to convert the API Blueprint docs to Open API v3.0, the script fails.
cat apiary.apib | npx apib2swagger --yaml --open-api-3 > swagger.yaml

TypeError: Cannot read properties of undefined (reading 'value')
    at setResponseSchema (/Users/userme/.npm/_npx/b8304055354efd5a/node_modules/apib2swagger/src/responses.js:92:28)
    at module.exports.processResponses (/Users/userme/.npm/_npx/b8304055354efd5a/node_modules/apib2swagger/src/responses.js:181:29)
    at swaggerOperation (/Users/userme/.npm/_npx/b8304055354efd5a/node_modules/apib2swagger/index.js:160:22)
    at swaggerPaths (/Users/userme/.npm/_npx/b8304055354efd5a/node_modules/apib2swagger/index.js:148:60)
    at /Users/userme/.npm/_npx/b8304055354efd5a/node_modules/apib2swagger/index.js:71:17
    at Array.forEach (<anonymous>)
    at /Users/userme/.npm/_npx/b8304055354efd5a/node_modules/apib2swagger/index.js:62:26
    at Array.forEach (<anonymous>)
    at module.exports.convertParsed (/Users/userme/.npm/_npx/b8304055354efd5a/node_modules/apib2swagger/index.js:57:8)
    at exports.convert (/Users/userme/.npm/_npx/b8304055354efd5a/node_modules/apib2swagger/index.js:200:23)

When I run the script without the --open-api-3 flag, the file is converted, but IDE indicates "Property 'oneOf' is not allowed" errors and the official SwaggerEditor detects problems for all the nullable - 'null' properties. I guess the problem could be caused by the nullable values which are not handled properly.

Generated Open API v2.0:

      homeAddress:
        oneOf:
          - $ref: '#/definitions/Address'
            description: homeAddress, response only
          - type: 'null'

The source document has more than 1300 lines and is private so I cannot post it. It is valid according the API blueprint specs.