If a `$ref` is not found, a `NoMethodError: any_of` may be found

[jamietanna]

     NoMethodError:
       undefined method `any_of' for #<OpenAPIParser::Schemas::Reference:0x0000000107195548>

[hlascelles]

We are seeing this too with:

          "tagging_strings": {
            "type": "array",
            "description": "A collection of strongs",
            "items": {
              "type": "string"
            },
            "example": [
              "foo",
              "bar"
            ]
          },

payload:

{
  "tagging_strings": ["baz"]
}

Stack:

undefined method `any_of' for #<OpenAPIParser::Schemas::Reference:0x000055eccf27f670>
openapi_parser-1.0.0/lib/openapi_parser/schema_validator.rb:98:in `validator'
openapi_parser-1.0.0/lib/openapi_parser/schema_validator.rb:74:in `validate_schema'
openapi_parser-1.0.0/lib/openapi_parser/schema_validator.rb:62:in `validate_data'
openapi_parser-1.0.0/lib/openapi_parser/schema_validator.rb:45:in `validate'
openapi_parser-1.0.0/lib/openapi_parser/schemas/media_type.rb:15:in `validate_parameter'
openapi_parser-1.0.0/lib/openapi_parser/schemas/request_body.rb:24:in `validate_request_body'
openapi_parser-1.0.0/lib/openapi_parser/schemas/operation.rb:25:in `validate_request_body'
openapi_parser-1.0.0/lib/openapi_parser/request_operation.rb:52:in `validate_request_body'