[heat] Issue happend during server_group creation with policies

Hi heat team. I reported the following bug report [1] on Sep 2. [1] https://storyboard.openstack.org/#!/story/2009164 Have you confirmed it? This error seems to appear to have occurred after patch [2] was merged. [2] https://review.opendev.org/c/openstack/heat/+/783971 Please kindly check it, thanks. Regards, Ayumu Ueha