Нужно нажав на кнопку удаления стереть всё с вьюхи. Кнопка находится на activity_main . Возникает null reference error

class MySurfaceView(context: Context?): View(context) {
    constructor(context: Context?, attrs: AttributeSet): this(context)

    private val paint = Paint(Paint.ANTI_ALIAS_FLAG)
    private val paintLine = Paint(Paint.ANTI_ALIAS_FLAG)

    private val path: Path?
    private val path2: Path?

    private var heightS = 0f
    private var widthS =  0f

    private var demenitions = 2

    @SuppressLint("ClickableViewAccessibility", "WrongViewCast")
    override fun onTouchEvent(event: MotionEvent): Boolean {


        if (event.action == MotionEvent.ACTION_DOWN) {
            path?.moveTo(event.x, event.y)
            path2?.moveTo(widthS - event.x, heightS - event.y)

        } else {
            path?.lineTo(event.x, event.y)
            path2?.lineTo(widthS - event.x, heightS - event.y)
        }

        invalidate()
        return true
    }

    override fun onDraw(canvas: Canvas) {
        when (demenitions) {
            2 -> canvas.drawLine(0f, heightS/2, widthS, heightS/2, paintLine)
        }
        if (path != null) canvas.drawPath(path, paint)
        if (path2 != null) canvas.drawPath(path2, paint)
    }

    fun deletePaths() {
        path?.reset()
        path2?.reset()
        invalidate()
    }

    init {
        path = Path()
        path2 = Path()
        print(context.toString())
        **b_del.setOnClickListener { deletePaths() }**

        paint.style = Paint.Style.STROKE
        paint.strokeWidth = 5f
        paint.color = Color.BLACK
    }

    override fun onCreateDrawableState(extraSpace: Int): IntArray {
        heightS = this.height.toFloat()
        widthS = this.width.toFloat()
        return super.onCreateDrawableState(extraSpace)
    }
}

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
    }

    override fun onResume() {
        super.onResume()
        main()
    }

    private fun main(){
        b_del.setOnClickListener {view2}
        Log.d("fwt","Fgdgdg")
    }
}