Only remove handlers from pipeline if future is successful

If the future is not successful the channel may have been closed. The
pipeline of a closed channel is empty, so attempting to remove handlers
from it would cause an exception.

Signed-off-by: Graham <gpe@openrs2.org>

game/src/main/kotlin/org/openrs2/game/net/login/LoginChannelHandler.kt

@@ -61,11 +61,13 @@ public class LoginChannelHandler @Inject constructor(
         )
         ctx.pipeline().remove(Rs2Decoder::class.java)
 
-        ctx.write(LoginResponse.Js5Ok).addListener {
+        ctx.write(LoginResponse.Js5Ok).addListener { future ->
+            if (future.isSuccess) {
                 ctx.pipeline().remove(Rs2Encoder::class.java)
                 ctx.pipeline().remove(this)
             }
         }
+    }
 
     private fun handleInitJaggrabConnection(ctx: ChannelHandlerContext) {
         ctx.pipeline().addLast(