protected function _initStackInstance()
    {
        $this->_title($this->__('System'))->_title($this->__('AOE Profiler'));

        $stackId = $this->getRequest()->getParam('stack_id', null);

        if ($stackId) {
            $stackInstance = Mage::getModel('aoe_profiler/run'); /* @var $stackInstance Aoe_Profiler_Model_Run */
            $stackInstance->load($stackId);
            if (!$stackInstance->getId()) {
                $this->_getSession()->addError(Mage::helper('aoe_profiler')->__('No data found with this id.'));
                return false;
            }
            Mage::register('current_stack_instance', $stackInstance);
            return $stackInstance;
        }
        return false;
    }