[ticket/12575] Fix the tests

PHPBB3-12575

phpBB/phpbb/di/service_collection.php

@@ -38,6 +38,14 @@ class service_collection extends \ArrayObject
 		return new service_collection_iterator($this->container, $this);
 	}
 
+	/**
+	* {@inheritdoc}
+	*/
+	public function offsetExists($index)
+	{
+		return parent::offsetExists($index);
+	}
+
 	/**
 	* {@inheritdoc}
 	*/