PHP notice in page title and name

Attached patch fixes this.

Another solution, though I didn't test, is in hook_commerce_checkout_page_info_alter() to check for all panes and change correspondant $pane['page'] to 'disabled'. However this need to be done in every hook implementation and is risky, because usually page_info is called before pane_info, if we get panes list in page_info_alter there is a change of dead lock.