Resolve issue where disconnect messages can get hidden when another packet is being sent (#906)

Author: onebeastchris

protocol/src/main/java/org/geysermc/mcprotocollib/network/session/NetworkSession.java

@@ -209,16 +209,20 @@ private void doSendPacket(@NonNull Packet packet, @Nullable Runnable onSent) {
         if (!sendingEvent.isCancelled()) {
             final Packet toSend = sendingEvent.getPacket();
             this.channel.writeAndFlush(toSend).addListener((ChannelFutureListener) future -> {
-                if (!future.isSuccess()) {
-                    return;
-                }
-
                 if (onSent != null) {
                     onSent.run();
                 }
 
-                callPacketSent(toSend);
-            }).addListener(ChannelFutureListener.FIRE_EXCEPTION_ON_FAILURE);
+                // See PacketSendListener#thenRun - runnable first, success check later
+                if (!future.isSuccess()) {
+                    // Mirrors Java client handling; uses a void promise when there's no runnable
+                    if (onSent != null) {
+                        channel.pipeline().fireExceptionCaught(future.cause());
+                    }
+                } else {
+                    callPacketSent(toSend);
+                }
+            });
         }
     }