Fixed exception when collection selects non-existent attribute in PR #2993 (#3038)

Author: davidhiendl

app/code/core/Mage/Eav/Model/Entity/Collection/Abstract.php

@@ -438,6 +438,10 @@ public function addAttributeToSelect($attribute, $joinType = false)
             } else {
                 $attrInstance = Mage::getSingleton('eav/config')
                     ->getAttribute($this->getEntity()->getType(), $attribute);
+                // failure to resolve an attribute from the eav config implies it does not exist
+                if (empty($attrInstance)) {
+                    return $this;
+                }
             }
             if (empty($attrInstance)) {
                 throw Mage::exception(