fix(server): allow null messages in RoomPacket

Author: xeruf

socha-sdk/src/server-api/sc/protocol/responses/RoomPacket.kt

@@ -10,5 +10,5 @@ import sc.protocol.requests.ILobbyRequest
 data class RoomPacket(
         @XStreamAsAttribute
         val roomId: String,
-        val data: ProtocolMessage
+        val data: ProtocolMessage?
 ): ILobbyRequest