* BOB, SAM, i2psnark: Fix datagram NPE (ticket #1275)

This could only happen on an extremely overloaded router.

apps/i2psnark/java/src/org/klomp/snark/dht/KRPC.java

@@ -1536,6 +1536,8 @@ public class KRPC implements I2PSessionMuxedListener, DHT {
         // TODO throttle
         try {
             byte[] payload = session.receiveMessage(msgId);
+            if (payload == null)
+                return;
             _rxPkts.incrementAndGet();
             _rxBytes.addAndGet(payload.length);
             if (toPort == _qPort) {