ensure avatars are always created

Following up on https://github.com/npm/newww/issues/240, here are a few users with avatars that don't currently show up on newww:

https://preview.npmjs.com/~jesusabdullah
https://preview.npmjs.com/~shtylman

I've added tests to the user presenter for this change, but am not sure how to smoke test it because we don't have user data in dev or staging. @rockbot can you think of a way?