fix: Keep empty meta from rendering a tag

[chaance]

Currently, if a meta key is null or undefined, we will render an empty tag. Our types also don't support an empty meta key, which is a bit annoying if you're working with optional data.

export function meta({ data }) {
  return {
    title: data.title, // always there, cool
    description: data.description // optional, don't bother with a tag but please don't yell at me!
  };
}

[kentcdodds]

I’ma superfan of this change 👍