I also found that bug in my ready-ecommerce site and fixed it
modules/order/views/order.php
line 59
replace parent::display($tpl);
with return parent::getContent($tpl);
modules/user/views/user.php
line 45
replace frame::_()->getModule(‘order’)->getView()->getAllOrders( $searchCriteria );
with return frame::_()->getModule(‘order’)->getView()->getAllOrders( $searchCriteria );