Warning: DOMXPath::query(): Invalid expression  in /var/www/vhosts/marijuana-seeds.nl/htdocs/public/app/code/local/Mana/Core/Helper/Js.php on line 54

#0 [internal function]: mageCoreErrorHandler(2, 'DOMXPath::query...', '/var/www/vhosts...', 54, Array)
#1 /var/www/vhosts/marijuana-seeds.nl/htdocs/public/app/code/local/Mana/Core/Helper/Js.php(54): DOMXPath->query('')
#2 /var/www/vhosts/marijuana-seeds.nl/htdocs/public/app/code/local/Mana/Core/Model/Observer.php(246): Mana_Core_Helper_Js->processFiles(Object(Mage_Catalog_CategoryController), Object(Mage_Core_Model_Layout))
#3 /var/www/vhosts/marijuana-seeds.nl/htdocs/public/app/code/core/Mage/Core/Model/App.php(1339): Mana_Core_Model_Observer->processJsCssFiles(Object(Varien_Event_Observer))
#4 /var/www/vhosts/marijuana-seeds.nl/htdocs/public/app/code/core/Mage/Core/Model/App.php(1318): Mage_Core_Model_App->_callObserverMethod(Object(Mana_Core_Model_Observer), 'processJsCssFil...', Object(Varien_Event_Observer))
#5 /var/www/vhosts/marijuana-seeds.nl/htdocs/public/app/Mage.php(448): Mage_Core_Model_App->dispatchEvent('controller_acti...', Array)
#6 /var/www/vhosts/marijuana-seeds.nl/htdocs/public/app/code/core/Mage/Core/Controller/Varien/Action.php(339): Mage::dispatchEvent('controller_acti...', Array)
#7 /var/www/vhosts/marijuana-seeds.nl/htdocs/public/app/code/core/Mage/Catalog/controllers/CategoryController.php(148): Mage_Core_Controller_Varien_Action->generateLayoutBlocks()
#8 /var/www/vhosts/marijuana-seeds.nl/htdocs/public/app/code/core/Mage/Core/Controller/Varien/Action.php(418): Mage_Catalog_CategoryController->viewAction()
#9 /var/www/vhosts/marijuana-seeds.nl/htdocs/public/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(254): Mage_Core_Controller_Varien_Action->dispatch('view')
#10 /var/www/vhosts/marijuana-seeds.nl/htdocs/public/app/code/core/Mage/Core/Controller/Varien/Front.php(172): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
#11 /var/www/vhosts/marijuana-seeds.nl/htdocs/public/app/code/core/Mage/Core/Model/App.php(354): Mage_Core_Controller_Varien_Front->dispatch()
#12 /var/www/vhosts/marijuana-seeds.nl/htdocs/public/app/Mage.php(684): Mage_Core_Model_App->run(Array)
#13 /var/www/vhosts/marijuana-seeds.nl/htdocs/public/index.php(105): Mage::run('base', 'website')
#14 {main}