private void updateHits() {
        DefaultErrorHit queryErrors = consumeAnyQueryErrors();
        if (queryErrors != null)
            add(queryErrors);
    }
Must be called before the list of hits, or anything dependent on the list of hits, is removed.
Consumes errors from the query if there is one set for this group
container-search/src/main/java/com/yahoo/search/result/HitGroup.java