mgr/dashboard: fix gateways section error:”404 - Not Found RGW Daemon not found:...

mgr/dashboard: fix gateways section error:”404 - Not Found RGW Daemon not found: None”

A case was missed here where we do have a default realm created but no default_zonegorup, in that case, the existing behavior should prevail and that's not being handled. If a default_realm is created but no default_zonegroup is there, weshould continue getting the keys from daemon_name = next(iter(daemon_keys))

Fixes: https://tracker.ceph.com/issues/68376
Signed-off-by: Aashish Sharma <aasharma@redhat.com>
(cherry picked from commit 8dd9e9dad6a5ad9b427d73c4547286fe46b67d46)