[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/forum.php

@@ -112,6 +112,8 @@ class forum extends \phpbb\feed\post_base
 			return false;
 		}
 
+		parent::fetch_attachments(array(), $topic_ids);
+
 		$this->sql = array(
 			'SELECT'	=>	'p.post_id, p.topic_id, p.post_time, p.post_edit_time, p.post_visibility, p.post_subject, p.post_text, p.bbcode_bitfield, p.bbcode_uid, p.enable_bbcode, p.enable_smilies, p.enable_magic_url, p.post_attachment, ' .
 							'u.username, u.user_id',