Safely access schema to prevent crashes

[makrandgupta]

Checklist

Hey, I just set up swagger on my repo and it kept crashing when trying to resolve params and path. This has fixed the issue for me. Wanted to put up this PR in case this is truly a bug. Tests are passing but dont see a benchmark script.

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[climba03003]

Please provide an unit test for the PR.

[makrandgupta]

I think the tests would go in test/spec/openapi/route.js. But I am not sure how to capture the change above in the way those tests are written. I could use some help here