NullReferenceException on a FSM attribute

I'm using like example the wiki FSM scripts (http://wiki.unity3d.com/index.php?title=Finite_State_Machine) to create a finite state machine.

     private FSMsystem fsm;
     
     float tempo;
     float timer=1.0f;
     
  
     public void SetTransition(Transition t) { fsm.realizaTransicao(t); }
  
     public void Start()
     {
         tempo=timer;
         iniciaFSM();
     }
  
     public void Update()
     {
         if(tempo==timer) //p mostrar uma mensagem d cada vez (mensagem e resposta)
             fsm.CurrentState.causaTransacao();
         
         
         tempo-=Time.deltaTime;
         
         if(tempo<0.0f)
         {
             fsm.CurrentState.realizaAcao();
             tempo=timer;
         }
     }
  
     private void iniciaFSM() //cria estados, adiciona transações, e adiciona estados à FSM
     {
         VitimaPotencialSempre stateVPS = new VitimaPotencialSempre();
         stateVPS.AddTransition(Transition.Iniciativa, StateID.TentaAmizade); 
  
         AmizadePedida stateAmizade = new AmizadePedida();
         stateAmizade.AddTransition(Transition.ProcessoConcluido, StateID.VPS);
  
         fsm = new FSMsystem();
         fsm.AddState(stateVPS);
         fsm.AddState(stateAmizade);
     }

However, at this my code above I got a NullReferenceException on the fsm (line 18) attribute and I don't understand why because on iniciaFSM function fsm is not null. Anyone know what I need to do to resolve this problem?