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

@@ -61,9 +61,11 @@ public class LoginChannelHandler @Inject constructor(
         )
         ctx.pipeline().remove(Rs2Decoder::class.java)
 
-        ctx.write(LoginResponse.Js5Ok).addListener {
-            ctx.pipeline().remove(Rs2Encoder::class.java)
-            ctx.pipeline().remove(this)
+        ctx.write(LoginResponse.Js5Ok).addListener { future ->
+            if (future.isSuccess) {
+                ctx.pipeline().remove(Rs2Encoder::class.java)
+                ctx.pipeline().remove(this)
+            }
         }
     }