How to fix "cannot get property 'info' on null object' when importing swagger

Thanks again - now you've put me on to the Open Source version I'll look into that!

By the way, (and to record it here for others searching for the same problem), the issue was to do with CORS which I had set up correctly on the AWS S3 service I was using to serve the .yaml file but an extension in my browser (unfortunately I have not been able to determine which one) was somehow blocking the Origin header and so the 

Access-Control-Allow-Origin header was not being returned.

In turn, the browser disallowed loading the resource.