Cannot use empty pump source with MapDB

MapDBEmptyPumpSource.java

import java.util.Iterator;

import org.mapdb.DB;
import org.mapdb.DBMaker;
import org.mapdb.Fun.Tuple2;

public class MapDBEmptyPumpSource {
	public static void main(String... args) {
		Iterator<Tuple2<String, String>> data = new Iterator () {
	
			@Override
			public boolean hasNext() {
				return false;
			}
	
			@Override
			public Object next() {
				return null;
			}
	
			@Override
			public void remove() {
				// TODO Auto-generated method stub
			}	
		};
		
		DB db = DBMaker.newTempFileDB()
				.make();
		
		db.createTreeMap("test")
			.pumpSource(data)
			.make();
	}	
}