[Cosmos] Fix ClassCastException when building CosmosException from an empty error response body

[marcellustavares]

Description

JsonSerializable.fromJson(String, ObjectMapper) performs an unchecked cast of the parsed tree to ObjectNode:

return (ObjectNode) objectMapper.readTree(json);

When json is empty or blank, ObjectMapper.readTree(...) returns a MissingNode (not an ObjectNode), so the cast throws ClassCastException: class ...MissingNode cannot be cast to class ...ObjectNode.

fixes #49322

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[github-actions]

Thank you for your contribution @marcellustavares! We will review the pull request and get back to you soon.

[marcellustavares]

@microsoft-github-policy-service agree company="Elastic"