fix error messages

[matthyk]

Fixes a bug where incorrect error messages were produced when using the path option instead of the url option for the route declaration with routemethod.

So

fastify.route({
      method: 'GET',
      path: '/test'
    })

would produce the error message: Missing handler function for GET:undefined route.

Checklist

• 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

[RafaelGSS]

LGTM.

[github-actions]

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