Don't send bungeecord plugin messages to the client

proxy/src/main/java/net/md_5/bungee/connection/DownstreamBridge.java

@@ -451,6 +451,8 @@ public class DownstreamBridge extends PacketHandler
                     con.getServer().sendData( "BungeeCord", b );
                 }
             }
+            
+            throw CancelSendSignal.INSTANCE;
         }
     }