Missed required parameter raises an error

[skryukov]

Scheme with required but not mentioned on parameter list attribute raises an error:

OpenapiValidator raises error
     Failure/Error: skip_error = processor.options[:response] && defined_properties[property]["writeOnly"]

     NoMethodError:
       undefined method `[]' for nil:NilClass

Example scheme:

paths:
  /pets/{id}:
    get:
      responses:
        '200':
          content:
            application/json:
              schema:
                required:
                  - id
                  - name
                properties:
                  id: { type: integer }