NetEase/pomelo-globalchannel-plugin — pull request #5 by qiankanglai (2014-06-17 15:58:07+00:00)
Title: pushMessage should return null,[]

If pushMessage is called in async.waterfall, we should ensure that cb is called in the same way!
we cannot invokeCallback(cb) or invokeCallback(cb, null, failIds) in the same function under different situations.

```
async.waterfall([
function(cb){
globalChannel.pushMessage("hybrid", "onCHAT", message, channel, null, cb);
},
function(fails, cb){
globalChannel.pushMessage("sio", "onCHAT", message, channel, null, cb);
}],
function(err){
}
);
```

If there is no hybrid connectors, the second function in waterfall will hold fails as callback and cb as undefined.