Fatal error: Uncaught Error: Call to a member function addAttributeToSelect() on null in /var/www/vhosts/trallefabrikken.no/httpdocs/app/code/core/Mage/Catalog/Model/Layer.php:119 Stack trace: #0 /var/www/vhosts/trallefabrikken.no/httpdocs/app/code/core/Mage/Catalog/Model/Layer.php(103): Mage_Catalog_Model_Layer->prepareProductCollection(NULL) #1 /var/www/vhosts/trallefabrikken.no/httpdocs/app/code/local/Amasty/Groupcat/Model/ObserverProduct.php(18): Mage_Catalog_Model_Layer->getProductCollection() #2 /var/www/vhosts/trallefabrikken.no/httpdocs/app/code/core/Mage/Core/Model/App.php(1358): Amasty_Groupcat_Model_ObserverProduct->handleLayoutRender(Object(Varien_Event_Observer)) #3 /var/www/vhosts/trallefabrikken.no/httpdocs/app/code/core/Mage/Core/Model/App.php(1337): Mage_Core_Model_App->_callObserverMethod(Object(Amasty_Groupcat_Model_ObserverProduct), 'handleLayoutRen...', Object(Varien_Event_Observer)) #4 /var/www/vhosts/trallefabrikken.no/httpdocs/app/Mage.php(451): Mage_Core_Model_App->dispatchEvent('controller_acti.. in /var/www/vhosts/trallefabrikken.no/httpdocs/app/code/core/Mage/Catalog/Model/Layer.php on line 119