fix: prevent error for undefined method on search results page

```
Fatal error: Uncaught Error: Call to undefined method Smile_ElasticSearch_Model_Resource_Engine_Elasticsearch::isLeyeredNavigationAllowed() in /var/www/html/app/code/core/Mage/CatalogSearch/Block/Layer.php:81 Stack trace: #0 /var/www/html/app/design/frontend/rwd/default/template/catalog/layer/view.phtml(34): Mage_CatalogSearch_Block_Layer->canShowBlock() #1 /var/www/html/app/code/core/Mage/Core/Block/Template.php(241): include('/var/www/html/a...') #2 /var/www/html/app/code/core/Mage/Core/Block/Template.php(273): Mage_Core_Block_Template->fetchView('frontend/rwd/de...') #3 /var/www/html/app/code/core/Mage/Core/Block/Template.php(287): Mage_Core_Block_Template->renderView() #4 /var/www/html/app/code/core/Mage/Core/Block/Abstract.php(923): Mage_Core_Block_Template->_toHtml() #5 /var/www/html/app/code/core/Mage/Core/Block/Text/List.php(43): Mage_Core_Block_Abstract->toHtml() #6 /var/www/html/app/code/core/Mage/Core/Block/Abstract.php(923): Mage_Core_Block_Text_List->_toHtml() #7 /var/www/html/app/code/core/Mage/Core/Block/Ab in /var/www/html/app/code/core/Mage/CatalogSearch/Block/Layer.php on line 81
```

refs #1

src/app/code/community/Smile/ElasticSearch/Model/Resource/Engine/Elasticsearch.php

@@ -329,6 +329,11 @@ public function isLayeredNavigationAllowed()
         return true;
     }
 
+    public function isLeyeredNavigationAllowed()
+    {
+        return $this->isLayeredNavigationAllowed();
+    }
+
     /**
      * Prepares index data.
      * Should be overriden in child classes if needed.