public void addErrorsFrom(HitGroup other) {
        ErrorHit otherErrorHit = other.getErrorHit();
        if (otherErrorHit != null) {
            for (ErrorMessage msg : otherErrorHit.errors()) {
                addError(msg);
            }
        }
    }
merge any errors from the other HitGroup into this
container-search/src/main/java/com/yahoo/search/result/HitGroup.java