SPIGOT-1055: Send empty string when RCON command is cancelled.

Drops the RemoteControlSession patch as the decompiled code is a mess.

nms-patches/DedicatedServer.patch

@@ -224,7 +224,7 @@
 +                RemoteServerCommandEvent event = new RemoteServerCommandEvent(remoteConsole, s);
 +                server.getPluginManager().callEvent(event);
 +                if (event.isCancelled()) {
-+                    return null;
++                    return "";
 +                }
 +                // Event change end
 +                ServerCommand serverCommand = new ServerCommand(event.getCommand(), RemoteControlCommandListener.getInstance());