Potential NPE in Muffler#digest when Message is not yet set

[mgrieder]

I had the following Exception with Version 1.0.0

Exception in thread "Timer-0" java.lang.NullPointerException
    at com.eclecticlogic.whisper.core.Muffler.digest(Muffler.java:88)
    at com.eclecticlogic.whisper.core.WhisperManager.run(WhisperManager.java:122)
    at java.util.TimerThread.mainLoop(Unknown Source)
    at java.util.TimerThread.run(Unknown Source)

This is a race condition and is possible when the TimerThread is running between queuesByMessage.putIfAbsent and muffler.log in WispherManager#log: then lastMessage is not yet set.
I think it is enough to add a check for a Null Message in Muffler#digest

[eclecticlogic]

I don't think it is a race condition. It is just a plain flaw in the logic. If there is one error message and that message is not suppressed, the next digest run would result in a NPE. I've put in a fix and released v1.0.1. It may take a couple of hours for the maven central repo to show the artifact in the index. Thanks for the bug report.