feat(Arguments#key?) also test #to_h for nil
feat(Arguments#key?) also test #to_h for nil

rmosolgo/graphql-ruby,xuorig/graphql-ruby,xuorig/graphql-ruby,xuorig/graphql-ruby,rmosolgo/graphql-ruby,rmosolgo/graphql-ruby,rmosolgo/graphql-ruby,nevesenin/graphql-ruby,nevesenin/graphql-ruby,nevesenin/graphql-ruby,nevesenin/graphql-ruby