Minor mistake in aggregation documentation for Fuse MR

public class MyAggregationStrategy implements AggregationStrategy {
    public Exchange aggregate(Exchange oldExchange, Exchange newExchange) {
        String oldBody =
            oldExchange.getIn().getBody(String.class);
        String newBody =
            newExchange.getIn().getBody(String.class);
        String concatBody = oldBody.concat(newBody);
        // Concatenate old and new.
        oldExchange.getIn().setBody(concatBody);
        // Ignore the message headers!
        // (in a real application, you would probably do
        //  something more sophisticated here).
        return oldExchange;
    }
}

public class MyAggregationStrategy implements AggregationStrategy {
    public Exchange aggregate(Exchange oldExchange, Exchange newExchange) {
        if (oldExchange == null) {
            // first time, the oldExchange is null, so just return newExchange as nothing to merge
            return newExchange;
        }

        String oldBody =
            oldExchange.getIn().getBody(String.class);
        String newBody =
            newExchange.getIn().getBody(String.class);
        String concatBody = oldBody.concat(newBody);
        // Concatenate old and new.
        oldExchange.getIn().setBody(concatBody);
        // Ignore the message headers!
        // (in a real application, you would probably do
        //  something more sophisticated here).
        return oldExchange;
    }
}