Update src/GraphQL.Client/GraphQLHttpClient.cs

Dispose if has value

Co-authored-by: Alexander Rose <[email protected]>

Author: Maydayof

src/GraphQL.Client/GraphQLHttpClient.cs

@@ -188,7 +188,7 @@ protected virtual void Dispose(bool disposing)
                 Debug.WriteLine($"Disposing GraphQLHttpClient on endpoint {Options.EndPoint}");
                 _cancellationTokenSource.Cancel();
                 HttpClient.Dispose();
-                _lazyHttpWebSocket?.Value.Dispose();
+                if(_lazyHttpWebSocket?.HasValue) _lazyHttpWebSocket?.Value.Dispose();
                 _cancellationTokenSource.Dispose();
             }
         }