First, option(OPTVIEWATTACH) is only set for (s->flags & DISPLAY), so that
check can be ignored.

With that removed, all this is doing is printing
  [-- This is an attachment ...]
with no context in the middle of non-display rendering for the case
$honor_disposition is set with a handler.

This makes no sense and I believe is a logic error.  Perhaps this
never took effect, but with $forward_attachments it now affects
forwarding in that case.