🐛 Rename variable

Fix variable name, the search engine has nothing to do with a default country in here

Author: avoelkl

app/code/Magento/CatalogSearch/Model/Adminhtml/System/Config/Backend/Engine.php

@@ -61,8 +61,8 @@ public function beforeSave()
         parent::beforeSave();
         $value = (string)$this->getValue();
         if (empty($value)) {
-            $defaultCountry = $this->engineResolver->getCurrentSearchEngine();
-            $this->setValue($defaultCountry);
+            $searchEngine = $this->engineResolver->getCurrentSearchEngine();
+            $this->setValue($searchEngine);
         }
         return $this;
     }