use BEACON_NOT_AVAILABLE to indicate beacon not found at position

src/de/tud/kom/p2psim/impl/topology/movement/resourceaware/ResourceCollectionMovementMonitor.java

@@ -150,7 +150,7 @@ public class ResourceCollectionMovementMonitor implements SimHostComponent, Loca
     }
 
     protected void beaconNotAvailable(UniqueID beaconId) {
-        notifyListener(beaconId, 0, ResourceCollectionListener.UNKNOWN_REMAINING_RESOURCES);
+        notifyListener(beaconId, 0, ResourceCollectionListener.BEACON_NOT_AVAILABLE);
     }
 
     /**