untrack objects, when you use the delete key

src/ui/view/GUI.java

@@ -439,6 +439,7 @@ public class GUI<E> implements CategoryListener {
 					UpperNodeCanvas uNC = (UpperNodeCanvas) ((JScrollPane) tabTemp.getSelectedComponent()).getViewport()
 							.getComponent(0);
 					for (AbstractCpsObject cps : model.getSelectedCpsObjects()) {
+						controller.removeTrackingObj(cps);
 						if (uNC.upperNode.getNodes().contains(cps)) {
 							controller.delObjUpperNode(cps, uNC.upperNode);
 							// Remove UpperNodeTab if UpperNode deleted
@@ -475,6 +476,7 @@ public class GUI<E> implements CategoryListener {
 					boolean save = false;
 					for (int j = 0; j < model.getSelectedCpsObjects().size(); j++) {
 						AbstractCpsObject cps = model.getSelectedCpsObjects().get(j);
+						controller.removeTrackingObj(cps);
 						if (j < model.getSelectedCpsObjects().size() - 1)
 							save = true;
 						controller.delCanvasObject(cps, save);