NetStore.getAsync will fail with NPE under certain conditions

[codepitbull]

I was trying to upgrade ethereumj to Netty 4.1 and found the following issue which I think is also a bug with the current version.
There is a DefaultPromise being constructed without an executor, sidestepping the actual intention of this class in Netty:
public synchronized Future<Chunk> getAsync(Key key) { Chunk chunk = localStore.get(key); Promise<Chunk> ret = new DefaultPromise<Chunk>() {};

Using the DefaultPromise this way only works because of a lucky combination of checks in Netty.
Due to another check in DefaultPromise.notifyListeners this issue only ever causes problems if a listener has been registered. This lucky combo is gone in Netty 4.1.

To see what I mean run BzzProtocolTest.simpleTest in the current version. The test will work.
Now update to Netty to 4.1.13 and run again and you will see the NPE.

I currently have no good idea what the correct executor might be in this situation.