FIX: clean preset_folder when logging out

Change-Id: I0a61db6b6ae0fc4bad1f178e1492384a42de1501
Signed-off-by: Stone Li <stone.li@bambulab.com>

src/slic3r/GUI/GUI_App.cpp

@@ -3096,6 +3096,7 @@ void GUI_App::request_user_logout()
 
         m_agent->user_logout();
         m_agent->set_user_selected_machine("");
+        app_config->set("preset_folder", "");
         /* delete old user settings */
         m_device_manager->clean_user_info();
         GUI::wxGetApp().sidebar().load_ams_list({});