public ErrorMessage getError() {
        updateHits();
        if (errorHit == null)
            return null;
        else
            return errorHit.errors().iterator().next();
    }
Returns the first error in this result,
or null if no searcher has produced an error AND the query doesn't contain an error
container-search/src/main/java/com/yahoo/search/result/HitGroup.java