qix Error Message with java mapscript

[Nicol Hermann]

Hi List

i have got a very simple map-file (one layer with a shapefile
datasource) and a java class which loads this map-file. See below.
When i execute this script without any further actions everything is
fine. 
When i execute the zoomRectangle method on it i got the following error
message:

Exception in thread "main" java.io.IOException: Unable to open spatial
index for /tmp/world.qix. In most cases you can safely ignore this
message, otherwise check file names and permissions.
	at edu.umn.gis.mapscript.mapscriptJNI.mapObj_draw(Native Method)
	at edu.umn.gis.mapscript.mapObj.draw(mapObj.java:397)
	at msjava.world.main(world.java:22)

Why did this error only occur when i execute the zoomRectangle method.
Is it always necessary to create the qix file (when i create the qix
file the error message disappear)?
Is this a bug?

Many thank for your help
Nicol


package msjava;
import edu.umn.gis.mapscript.*;

public class world {
        public static void main(String[] args)  {
           world w = new world();
           System.loadLibrary("mapscript");
           imageObj bild;

           mapObj map = new mapObj("/tmp/world.map");
           w.zoomRect(map, "230 328 288 397");
           bild = map.draw();
           bild.save("/tmp/test.png", map);
           bild.delete();
        }

        public void zoomRect(mapObj map, String imgbox) {
            rectObj img = getRectObj(imgbox);
            double minY = img.getMiny();
            double maxY = img.getMaxy();
            img.setMaxy(minY);
            img.setMiny(maxY);
            map.zoomRectangle(img, map.getWidth(), map.getHeight(),
map.getExtent(),null);
        }

        public static rectObj getRectObj(String coords) {
          String[] sImgrect = coords.split(" ");
          rectObj rectObj = new
rectObj(Float.parseFloat(sImgrect[0]),Float.parseFloat(sImgrect[1]),Float.parseFloat(sImgrect[2]
),Float.parseFloat(sImgrect[3]),mapscript.MS_FALSE);
          return rectObj;
        }
}