Fix racing

regression by 5cf880586de442233aa87d58d254112c00b15551
Deobfuscate NewPacketFormatKeyContext.ack()

1. lostBeforeAcked == !validAck
2. { ... if(...) { ... return; } else { ... } ... } hurts eyes.
3. if pn == null, then throttle == null
Merge branch 'eleriseth-patches' into next