Issue #1591678 by recrit, damiankloip, tim.plunkett: Ensure that entity_type...

Issue #1591678 by recrit, damiankloip, tim.plunkett: Ensure that entity_type isset on the results object in views_handler_field_field::post_execute().

modules/field/views_handler_field_field.inc

@@ -639,7 +639,7 @@ function post_execute(&$values) {
       $entities_by_type = array();
       $revisions_by_type = array();
       foreach ($values as $key => $object) {
-        if (isset($object->{$this->aliases['entity_type']}) && isset($object->{$this->field_alias}) && !isset($values[$key]->_field_data[$this->field_alias])) {
+        if (isset($this->aliases['entity_type']) && isset($object->{$this->aliases['entity_type']}) && isset($object->{$this->field_alias}) && !isset($values[$key]->_field_data[$this->field_alias])) {
           $entity_type = $object->{$this->aliases['entity_type']};
           if (empty($this->definition['is revision'])) {
             $entity_id = $object->{$this->field_alias};