Warning: Missing argument 1 for Mage_Core_Model_Layout_Update::addUpdate(), called in /home/anylinux/public_html/demo/app/code/community/Alw/Brand/Model/Observer.php on line 20 and defined  in /home/anylinux/public_html/demo/app/code/core/Mage/Core/Model/Layout/Update.php on line 105

#0 /home/anylinux/public_html/demo/app/code/core/Mage/Core/Model/Layout/Update.php(105): mageCoreErrorHandler(2, 'Missing argumen...', '/home/anylinux/...', 105, Array)
#1 /home/anylinux/public_html/demo/app/code/community/Alw/Brand/Model/Observer.php(20): Mage_Core_Model_Layout_Update->addUpdate()
#2 /home/anylinux/public_html/demo/app/code/core/Mage/Core/Model/App.php(1338): Alw_Brand_Model_Observer->changeLayoutEvent(Object(Varien_Event_Observer))
#3 /home/anylinux/public_html/demo/app/code/core/Mage/Core/Model/App.php(1317): Mage_Core_Model_App->_callObserverMethod(Object(Alw_Brand_Model_Observer), 'changeLayoutEve...', Object(Varien_Event_Observer))
#4 /home/anylinux/public_html/demo/app/Mage.php(448): Mage_Core_Model_App->dispatchEvent('controller_acti...', Array)
#5 /home/anylinux/public_html/demo/app/code/core/Mage/Core/Controller/Varien/Action.php(339): Mage::dispatchEvent('controller_acti...', Array)
#6 /home/anylinux/public_html/demo/app/code/core/Mage/Core/Controller/Varien/Action.php(269): Mage_Core_Controller_Varien_Action->generateLayoutBlocks()
#7 /home/anylinux/public_html/demo/app/code/community/Alw/Brand/controllers/IndexController.php(24): Mage_Core_Controller_Varien_Action->loadLayout()
#8 /home/anylinux/public_html/demo/app/code/core/Mage/Core/Controller/Varien/Action.php(418): Alw_Brand_IndexController->viewAction()
#9 /home/anylinux/public_html/demo/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(254): Mage_Core_Controller_Varien_Action->dispatch('view')
#10 /home/anylinux/public_html/demo/app/code/core/Mage/Core/Controller/Varien/Front.php(172): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
#11 /home/anylinux/public_html/demo/app/code/core/Mage/Core/Model/App.php(354): Mage_Core_Controller_Varien_Front->dispatch()
#12 /home/anylinux/public_html/demo/app/Mage.php(684): Mage_Core_Model_App->run(Array)
#13 /home/anylinux/public_html/demo/index.php(87): Mage::run('', 'store')
#14 {main}