qapi: Fix regression with '-netdev help' Commit e36c714e causes 'qemu -netdev help' to dump core, because the call to visit_end_union() is no longer conditional on whether *obj was allocated. Reported by Marc-André Lureau <marcandre.lureau@gmail.com> Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1444861825-19256-1-git-send-email-eblake@redhat.com> [Commit message tweaked to say 'help' instead of '?'] Signed-off-by: Markus Armbruster <armbru@redhat.com>