ReplicationStatistics has ConcurrentHashMap entrySet problem

public String toString()
{
StringBuffer tmp = new StringBuffer();
HashMap copy = new HashMap(ctxStats);
Iterator iter = copy.entrySet().iterator();
while( iter.hasNext() )
{
Map.Entry entry = (Map.Entry) iter.next();
TimeStatistic stat = (TimeStatistic) entry.getValue();
tmp.append("[sessionID: ");
tmp.append(entry.getKey());
tmp.append(", replicationCount=");
tmp.append(stat.replicationCount);

stat could be null