Fix some linter issues

[blocknotes]

Hey :)

Checking with @redocly/openapi-cli linter I get some errors:

• Expected type string but got null related to the tags key when an empty value is exported;
• Operation object summary must be non-empty string. related to the summary key when an empty value is exported.

This PR is a proposal for minor improvements.

Please let me know your opinion.

[k0kubun]

Could we possibly add tests for this thing?

[blocknotes]

Could we possibly add tests for this thing?

Ok, if you run the spec only with the first commit (Add a test with a block route) you get this error:

# bundle exec rspec

         1) Extra routes #test_block returns the block content
            Failure/Error: tags = [route.requirements[:controller].classify]

            NoMethodError:
              undefined method `classify' for nil:NilClass
            # ./lib/rspec/openapi/record_builder.rb:24:in `build'
            # ./lib/rspec/openapi/hooks.rb:14:in `block in <top (required)>'

If you run the spec on the second commit (Skip empty tags and fix routes without a Rails controller) it will produce an OpenAPI YAML with an empty summary.

I removed the last commit (When a route is not found print a warning in place of an exception) to make some extra checks.