Apparently draft sometimes gets unhappy when you try to move to the end of an empty state, so only move to the end if we actually created a non-empty state. This will be irrelevant once https://github.com/matrix-org/matrix-react-sdk/pull/1890 is merged, but I have the fix now, and this is probably otherwise going to annoy me now I'm doing things where devtools is very useful. Fixes https://github.com/vector-im/riot-web/issues/6436