Buid problems

Hi there, I am new in unity like many others.
I made some scene with 6-7 scripts.
Everything is good in play mode, but when I build game it’s not working properly.
After that eaven play mod is corupted, and I have to reinstal unity and rebuild scene.
I have seen ppl said that problem could be in output_log file.
My output_log file is prety full of something, there are some parts.

**(Filename: C:/BuildAgent/work/812c4f5049264fad/Runtime/ExportGenerated/StandalonePlayer/UnityEngineDebug.cpp Line: 43)
NullReferenceException: Object reference not set to an instance of an object
at LightningScr.Update () [0x00000] in :0

(Filename: Line: -1)
NullReferenceException: Object reference not set to an instance of an object
at FireBallScr.Update () [0x00000] in :0

(Filename: Line: -1)**

and here is script that is refered to

#pragma strict

var projectile : GameObject;
var coolDownFireBall : float = 5;
var speed : float = 7;
var startCD = 3;
static var fireBallCd = false;
internal var nextFireBall : float;
internal var pucano = false;
internal var pucanje = false;

function Start () {

nextFireBall = startCD;

}

function Update () {

pucanje = KlikniPucaj.fireBallReady && KlikniPucaj.misVanMenija;
fireBallCd = Time.time > nextFireBall;
if (Input.GetButton ("Fire1") && fireBallCd && pucanje) {
	pucano = true;
	return;
	}

if (pucano) {
	nextFireBall = Time.time + coolDownFireBall;
	var clone : GameObject = Instantiate (projectile, transform.position, transform.rotation);
	clone.rigidbody.velocity = transform.TransformDirection(Vector3 (0,0,speed));
	Physics.IgnoreCollision(clone.collider, transform.root.collider);
	pucano = false;
	pucanje = false;
	}

}

Those lines are repeted many times, and something more.
Any help would be much apreciated.

Fixed it. It was NullReferenceExeption.