gistfile1.cs

    public class NullJsonHandler : DelegatingHandler
    {
        protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
        {

            var response = await base.SendAsync(request, cancellationToken);
            if (response.Content == null)
            {
                response.Content = new StringContent("{}");
            } else if (response.Content is ObjectContent)
            {
                var objectContent = (ObjectContent) response.Content;
                if (objectContent.Value == null)
                {
                    response.Content = new StringContent("{}");
                }
                
            }
            return response;
        }
    }