Simplify code at a few places

Remove some duplicate checks,
and unnecessary errors.
> Why?

Why what? 

Why add an empty target? Not to kill the next for cycle.

> I know there were assumptions in Annotator at some point that required annotations to have ranges, but do we have a requirement anywhere that the target property exist?

I don't think so.

>  I thought we used guards everywhere so that we didn't.

I am not sure. And empty array won't hurt.

I am not even sure when we have this situation.
Obviously not when creating a real annotations.
If we had this with replies and such, we would have seen these errors, but we have not.
Probably does not ever happen, for some reason.