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

Hello everyone,

I just purchased Top-Down Dungeons [Mobile] and added all my game prefabs correctly. But when I try to walk (move) with my player, I get this fatal error:

NullReferenceException: Object reference not set to an instance of an object
PlayerScript.CheckTerrain () (at Assets/Scripts/PlayerScript.js:162)
PlayerScript.MovePlayer () (at Assets/Scripts/PlayerScript.js:200)
PlayerScript.FixedUpdate () (at Assets/Scripts/PlayerScript.js:41)

Can anyone help me to fix this?

159-164 lines:

function CheckTerrain() {
	var MoveTarget = GameObject.Find("MoveTarget").transform.position;
	var MyY = transform.position;
	if (Terrain.activeTerrain.SampleHeight(MoveTarget) -1 > Terrain.activeTerrain.SampleHeight(MyY)) return false;
	else return true;
}

191-204 lines:

if (Input.GetKey ("mouse 1")) {
			if (Input.mousePosition.x >= Screen.width - Screen.width/6) { if (!animation.IsPlaying("idle")) AnimationPlay("idle"); return; }
		    playerPlane = new Plane(Vector3.up, transform.position);
       		ray = GameObject.Find("Main Camera").camera.ScreenPointToRay (Input.mousePosition);
       		hitdist = 0.0;
       		if (playerPlane.Raycast (ray, hitdist)) {
       			targetPos = Vector3(ray.GetPoint(hitdist).x,0,ray.GetPoint(hitdist).z);
				transform.rotation = Quaternion.LookRotation(targetPos - Vector3(transform.position.x,0,transform.position.z));
				if (Vector3.Distance(targetPos,transform.position)<9) { animName = "walk"; speed = 5; } else { animName = "run"; speed = 12; }
				if (MoveCanSee() == true && CheckTerrain() == true) transform.Translate(Vector3.forward * Time.deltaTime * speed);
				if (IsMultiplayer == 1) UpdateTransform();
			}
	if (!animation.IsPlaying(animName)  && !animation.IsPlaying("spellcast")) AnimationPlay(animName);
}

and 39-42 lines:
function FixedUpdate () {
if (IsMultiplayer == 1 && nextCheckMP < Time.time) { nextCheckMP = Time.time + 1; CheckMP(); }
if (Died == 0) MovePlayer();
}

Line 162 of your PlayerScript.js uses a variable called Terrain. This variable hasn’t been initialised.