material modification : start with current material

src/main/java/fr/ill/ics/n3d/gui/EditorMenuBar.java

@@ -781,7 +781,7 @@ public class EditorMenuBar extends MenuBar {
     			if (Nomad3DEditor.getInstance().getModel() == null || Nomad3DEditor.getInstance().getModel().getSelection().isEmpty()) {
     				return;
     			}
-    			PhongMaterial oldMaterial = Component.DEFAULT_MATERIAL;
+    			PhongMaterial oldMaterial = Nomad3DEditor.getInstance().getModel().getSelection().iterator().next().getMaterial();
 
     			GridPane scenePane = new GridPane();
     			scenePane.setAlignment(Pos.CENTER);