Proxy Generation on client is failing. #93

This was working fine for a while. I can open the Proxy path in browser and see the generated text. However, compiling the proxy I'm getting the following error, this issue started recently. How can I fix it?

Error 5 The "ProxyGenerationTask" task failed unexpectedly. System.ArgumentNullException: Value cannot be null.
Parameter name: objectToConvert
at WebApiProxy.Tasks.ProxyGenerationTask.Execute()
at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute()
at Microsoft.Build.BackEnd.TaskBuilder.d__20.MoveNext()