NPE when invoke asynchronously use JdkProxy.

[ujjboy]

It will throw NPE when invoke asynchronously use JDKProxy. the demo case like this:

public interface AllTypeService {
    public int echoInt(int i);
}

ConsumerConfig<AllTypeService> aConsumer = new ConsumerConfig<AllTypeService>()
       .setInterfaceId(AllTypeService.class.getName())
       .setProxy("jdk")
       .setInvokeType(RpcConstants.INVOKER_TYPE_FUTURE)
AllTypeService helloService2 = aConsumer.refer();
helloService2.echoInt(1); // will throw NPE 

The reason for this bug is appResponse of SofaResponse is null when async invoke. We need set default return value when the return type is primitive class.

PS: JavassistProxy is ok.