Centralize retained delete confirmation closing

src/node_dialog_open.cpp

@@ -60,7 +60,7 @@ void NodeDialogOpen::init_controls()
                 image_tex->tex.reset();
             }
             Asset::delete_file(path);
-            msgbox->destroy();
+            pp::panopainter::close_legacy_dialog_node(*msgbox);
         };
         (void)pp::panopainter::attach_legacy_overlay_node_to_root(*this, msgbox);
         root()->update();