Merge pull request koush#209 from robUx4/endcallback_npe_fix

Crash fix for a case where the EndCallback is not set and used

Author: koush

AndroidAsync/src/com/koushikdutta/async/BufferedDataEmitter.java

@@ -32,7 +32,7 @@ public void onDataAvailable() {
         if (mDataCallback != null && !mPaused && mBuffers.remaining() > 0)
             mDataCallback.onDataAvailable(this, mBuffers);
 
-        if (mEnded && mBuffers.remaining() == 0)
+        if (mEnded && mBuffers.remaining() == 0 && mEndCallback != null)
             mEndCallback.onCompleted(mEndException);
     }