[livibetter]

Okay. I finally got it. I think this is a bug of bbPress.

line 29-55 in rss.php ensures there is a post found at least, if not then die().

Normally, we see no entries in a feed if there is no posts matched. But bbPress choose to die. You can replace each line of die(); with a dummy statement like

1; // die();

However, this is no enough. The third statement from bottom:

bb_send_304( $posts[0]->post_time );

Replace it with

if ($posts)

bb_send_304( $posts[0]->post_time );

Since bbPress can’t find any posts, therefore it has no way to decide that should it send a 304.

Can anyone confirm this is a bug about choosing to die?