Fatal error: Call to a member function getBackend() on a non-object in app/code/core/Mage/Eav/Model/Entity/Abstract.php on line 1536.The error appears after SUPEE-10888 installation or after upgrade to Magento 188.8.131.52 or newer.
CauseSUPEE-10888 adds new attribute in database (`rp_customer_id`), without such attribute the model can not be loaded.
SolutionFlush Magento cache to execute database upgrade script (i.e. app/code/core/Mage/Customer/sql/customer_setup/upgrade-184.108.40.206.4.1.2-220.127.116.11.4.1.3.php for Magento 18.104.22.168).
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