Added call to schedule_background_process() when deleting modifier attribute

src/slic3r/GUI/GUI_ObjectSettings.cpp

@@ -85,6 +85,7 @@ void ObjectSettings::update_settings_list()
 #endif // __WXMSW__
 			btn->Bind(wxEVT_BUTTON, [opt_key, config, this](wxEvent &event) {
 				config->erase(opt_key);
+                wxGetApp().obj_list()->part_settings_changed();
                 wxTheApp->CallAfter([this]() {
                     wxWindowUpdateLocker noUpdates(m_parent);
                     update_settings_list();