usesFirestoreDocData stuck in `status: "loading"` if data does not exist

[jhuleatt]

Originally posted by @namiwang in https://github.com/FirebaseExtended/reactfire/discussions/438#discussioncomment-1251839

Expected behavior

{
  // ...
  status: "success",
  data: undefined,
  // ...
}

Actual behavior

{
  // ...
  status: "loading",
  data: undefined,
  // ...
}