[ticket/14838] Do not query full attachments table in feeds

The fetch_attachments() will also now throw a runtime exception if a feed
tries to do this nonetheless.

PHPBB3-14838

phpBB/phpbb/feed/overall.php

@@ -52,6 +52,8 @@ class overall extends \phpbb\feed\post_base
 			return false;
 		}
 
+		parent::fetch_attachments(array(), $topic_ids);
+
 		// Get the actual data
 		$this->sql = array(
 			'SELECT'	=>	'f.forum_id, f.forum_name, ' .