tweak#: Do not increment packet loss for unacknowledged packets

Packets can arrive out of order or not be sent at all (due to recent changes and "packet stuffing") and this results in false packet loss increase with the recent changes.

It could also result in the packets being "double counted" for packet loss, due to another packet increment being when the packet wait time expires

LiteNetLib/ReliableChannel.cs

@@ -197,17 +197,17 @@ private void ProcessAck(NetPacket packet)
                         break;
                     }
 
+                    ref var pendingPacket = ref _pendingPackets[pendingSeq % _maxWindowSize];
+
+                    // This packet isn't sent at all, we ignore it
+                    if (!pendingPacket.IsSent)
+                        continue;
+
                     int pendingIdx = pendingSeq % _maxWindowSize;
                     int currentByte = NetConstants.ChanneledHeaderSize + pendingIdx / BitsInByte;
                     int currentBit = pendingIdx % BitsInByte;
                     if ((acksData[currentByte] & (1 << currentBit)) == 0)
                     {
-                        if (Peer.NetManager.EnableStatistics)
-                        {
-                            Peer.Statistics.IncrementPacketLoss();
-                            Peer.NetManager.Statistics.IncrementPacketLoss();
-                        }
-
                         //Skip false ack
                         NetDebug.Write($"[PA]False ack: {pendingSeq}");
                         continue;