Magento – Notice: Trying to get property of non-object

Use the following script to list product attributes with non-existant backend models:

umask(0);
require 'app/Mage.php';    
Mage::setIsDeveloperMode(true);
Mage::app('admin');

$entityType = Mage::getSingleton('eav/config')->getEntityType('catalog_product');
foreach ($entityType->getAttributeCollection() as $attribute) {
    if ($backendClass = $attribute->getBackendModel()) {
        try {
            class_exists(Mage::getConfig()->getModelClassName($backendClass), true);
        } catch (Exception $e) {
            echo "Not found the backend model {$backendClass} for product attribute {$attribute->getAttributeCode()}\n";
        }
    }
}

Try clearing cache, and check file permissions are correctly set,

Directories : 755

Files : 644

Else another alternative is Reinstall Magento and do following steps:

It may solve the issue, but suggested to have round of research before doing and surely back up database:

Before to import database : - Add query

1) SET SQL_MODE=”NO_AUTO_VALUE_ON_ZERO”; 

OR

at beginning of sql import script

After import / installation : - Execute following query

2) SET FOREIGN_KEY_CHECKS = 0;
   UPDATE `core_store` SET `store_id` = 0 WHERE `code` like 'admin';
   UPDATE `core_website` SET `website_id` = 0 WHERE `code` like 'admin';
   UPDATE `customer_group` SET `customer_group_id` = 0 WHERE `customer_group_code` like 'NOT LOGGED IN';
   SET FOREIGN_KEY_CHECKS = 1;