google-cloud-node: Fail on subscription.exists request

Hi, after updating to v0.32.0 we are facing a very odd problem:

When we call the pubSub module for checking the existence of a subscription whith the current code:

    subscription.exists((error, exists) => {
        if(error){
            return callback(error);
        }
        if(exists){
            subscription.delete((error) => {
                if (error) {
                    return callback(error);
                }
                return callback(null);
            });
        }
        callback(null);
    }); 

we obtain an uncaught exception that breaks the execution.

  events.js:160
  throw er; // Unhandled 'error' event
      ^
  Error: Not Found
  at /Users/massimilianodelia/project/node_modules/grpc/src/node/src/client.js:411:17

we tried to surround exists function with try/catch but it doesn’t work. we are on node 6

please advise for any suggestion or workaround.