diff -u -r1.1 -r1.2
--- DisplayHitModules.java	10 Jan 2008 00:57:58 -0000	1.1
+++ DisplayHitModules.java	11 Feb 2008 22:47:53 -0000	1.2
@@ -81,19 +81,23 @@

             //get the right sensor
             IIdentifier id = new Identifier(h.getCellID()); 
             IDetectorElementContainer de = DetectorElementStore.getInstance().find(id); 

-            IDetectorElement sensor = de.get(0);

-            //make sure we don't have repeats
-            Integer hash = Integer.valueOf(sensor.hashCode());
-            if (alreadyMade.contains(hash)) continue; 
-            alreadyMade.add(hash); 

+            if (de.size() > 0)
+            {
+            	IDetectorElement sensor = de.get(0);

-            //get the module from the sensor 
-            IDetectorElement module = sensor.getParent(); 

+            	//make sure we don't have repeats
+            	Integer hash = Integer.valueOf(sensor.hashCode());
+            	if (alreadyMade.contains(hash)) continue; 
+            	
+            	alreadyMade.add(hash); 

-            drawPolyhedron(sensor,typeS,instanceTree,factory); 
-            drawPolyhedron(module,typeM,instanceTree,factory); 

+            	//get the module from the sensor 
+            	IDetectorElement module = sensor.getParent(); 

+            	drawPolyhedron(sensor,typeS,instanceTree,factory); 
+            	drawPolyhedron(module,typeM,instanceTree,factory); 
+            }

         }
     }