**_{_{}} Check the endpoint-list response before using its value** #678

Check the endpoint-list response before using its value

If Catchup Service returns a non-success response such as 401 or 500, SendJsonAsync deliberately leaves Value null, but this dereference immediately throws NullReferenceException. That makes EventStoreSetup crash instead of returning the service's actionable status; validate IsSuccessStatusCode and Value before enumerating it (and do the same for the refreshed endpoint and subscription-configuration responses).

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Originally posted by @chatgpt-codex-connector[bot] in #677 (comment)