fix: ensure error response properly serialized (#80)

Co-authored-by: ferhat elmas <[email protected]>

Author: peterdeme

src/StreamException.cs

@@ -58,7 +58,7 @@ internal static StreamException FromResponse(RestResponse response)
             // {"code": 6, "detail": "The following feeds are not configured: 'secret'", "duration": "4ms", "exception": "FeedConfigException", "status_code": 400}
             ExceptionResponse state = null;
 
-            if (!string.IsNullOrWhiteSpace(response.Content))
+            if (!string.IsNullOrWhiteSpace(response.Content) && response.Content.TrimStart().StartsWith("{"))
             {
                 state = StreamJsonConverter.DeserializeObject<ExceptionResponse>(response.Content);
             }