Function parameter cant be referenced

I have made a function and am calling it from a UI button. The function is supposed to change a string based on the string parameter, that is passed through that function.

Heres the code and heres what the button is set to do BUTTON. the button works as the console print clicked. I shouldnt need this but the errors are at the bottom.

 using UnityEngine;
 using System.Collections;
 
 public class CharacterSelect : MonoBehaviour {
     public PlayerController PlayController;
 
     // Use this for initialization
     void Start () {
         PlayController = GetComponent("PlayerController")as PlayerController;
     }
     
     // Update is called once per frame
     void Update () {
     
     }
     public void ChangeCharacter(string name)
     {
         print("CLICKED");
 
         PlayController.charName = name;
         Application.LoadLevel("Demo_LVL");
 
     }
 
 }


  NullReferenceException: Object reference not set to an instance of an object

CharacterSelect.ChangeCharacter (System.String name) (at Assets/CharacterSelect.cs:20) UnityEngine.Events.InvokableCall`1[System.String].Invoke (System.Object[] args) (at C:/buildslave/unity/build/Runtime/Export/UnityEvent.cs:141) UnityEngine.Events.CachedInvokableCall`1[System.String].Invoke (System.Object[] args) (at C:/buildslave/unity/build/Runtime/Export/UnityEvent.cs:259) UnityEngine.Events.InvokableCallList.Invoke (System.Object[] parameters) (at C:/buildslave/unity/build/Runtime/Export/UnityEvent.cs:575) UnityEngine.Events.UnityEventBase.Invoke (System.Object[] parameters) (at C:/buildslave/unity/build/Runtime/Export/UnityEvent.cs:717) UnityEngine.Events.UnityEvent.Invoke () (at C:/buildslave/unity/build/Runtime/Export/UnityEvent_0.cs:53) UnityEngine.UI.Button.Press () (at C:/buildslave/unity/build/Extensions/guisystem/UnityEngine.UI/UI/Core/Button.cs:35) UnityEngine.UI.Button.OnPointerClick (UnityEngine.EventSystems.PointerEventData eventData) (at C:/buildslave/unity/build/Extensions/guisystem/UnityEngine.UI/UI/Core/Button.cs:44) UnityEngine.EventSystems.ExecuteEvents.Execute (IPointerClickHandler handler, UnityEngine.EventSystems.BaseEventData eventData) (at C:/buildslave/unity/build/Extensions/guisystem/UnityEngine.UI/EventSystem/ExecuteEvents.cs:52) UnityEngine.EventSystems.ExecuteEvents.Execute[IPointerClickHandler] (UnityEngine.GameObject target, UnityEngine.EventSystems.BaseEventData eventData, UnityEngine.EventSystems.EventFunction`1 functor) (at C:/buildslave/unity/build/Extensions/guisystem/UnityEngine.UI/EventSystem/ExecuteEvents.cs:269) UnityEngine.EventSystems.EventSystem:Update()