cf v240, diego 0.1481.0, cflinuxfs-rootfs 1.21.0, etcd 63, garden-linux 0.339.0, bosh-openstack-kvm-ubuntu-trusty-go_agent 3262.4

With a runner instance, pushing the sample go application works fine.
Setting the default backend to diego, I assume the runner is no longer needed.
Set the runner to 0, results in a failed push:
Server error, status code: 404, error code: 250003, message: The stack could not be found: The requested app stack cflinuxfs2 is not available on this system.
Put the runner back, all appears good. I have a few environments running default diego, however, they all have at least 1 runner.

I've got some more verifying to see what's going, however, thought I would toss the question out.