fix: `invalid_input` API errors may not return details [Backport release-1.x]

[github-actions[bot]]

The create uploaded certificate endpoint may return the following error:

{
  "error": {
    "code": "invalid_input",
    "message": "certificate must use larger key size"
  }
}

This change ensure that we do not get a json unmarshal error (unexpected end of json) while trying to parse a non-existing details data.

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Backport ca78af2af8acd375460c0f9705ea9d62d5ee1cc4 from #507.

BEGIN_COMMIT_OVERRIDE fix: invalid_input API errors may not return details END_COMMIT_OVERRIDE