I am getting following exception.log file whenever i try to visit the category pages
2016-08-12T14:36:10+00:00 ERR (3):
exception 'Mage_Core_Exception' with message 'Invalid block type: ' in /home/magento/app/Mage.php:596
Stack trace:
#0 /home/magento/var/cache/ew/files/00/15/Mage/Core/Model/Layout.php(514): Mage::throwException('Invalid block t...')
#1 /home/magento/var/cache/ew/files/00/15/Mage/Core/Model/Layout.php(456): Mage_Core_Model_LayoutOverriddenClass->_getBlockInstance('', Array)
#2 /home/magento/var/cache/ew/files/00/15/Mage/Core/Model/Layout.php(491): Mage_Core_Model_LayoutOverriddenClass->createBlock('', 'product_list')
#3 /home/magento/var/cache/ew/files/00/15/Mage/Core/Model/Layout.php(258): Mage_Core_Model_LayoutOverriddenClass->addBlock('', 'product_list')
#4 /home/magento/var/cache/ew/files/00/15/Mage/Core/Model/Layout.php(224): Mage_Core_Model_LayoutOverriddenClass->_generateBlock(Object(Mage_Core_Model_Layout_Element), Object(Mage_Core_Model_Layout_Element))
#5 /home/magento/var/cache/ew/files/00/15/Mage/Core/Model/Layout.php(229): Mage_Core_Model_LayoutOverriddenClass->generateBlocks(Object(Mage_Core_Model_Layout_Element))
#6 /home/magento/app/code/core/Mage/Core/Controller/Varien/Action.php(344): Mage_Core_Model_LayoutOverriddenClass->generateBlocks()
#7 /home/magento/app/code/core/Mage/Catalog/controllers/CategoryController.php(148): Mage_Core_Controller_Varien_Action->generateLayoutBlocks()
#8 /home/magento/app/code/core/Mage/Core/Controller/Varien/Action.php(418): Mage_Catalog_CategoryController->viewAction()
#9 /home/magento/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(254): Mage_Core_Controller_Varien_Action->dispatch('view')
#10 /home/magento/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/magento/app/code/core/Mage/Core/Model/App.php(365): Mage_Core_Controller_Varien_Front->dispatch()
#12 /home/magento/app/Mage.php(685): Mage_Core_Model_App->run(Array)
#13 /home/magento/index.php(84): Mage::run('', 'store')
#14 {main}
i dont understand why this is happening on the simple category pages.
How to debug this issue.
