         _currentDigit = _nextDigit;
         _nextDigit = digit;
         currentFrame = 1;
-        displayLink.paused = false;
+        displayLink?.paused = false;
     }
     
     public func animateToDigit_withCABasicAnimation(digit: Int) {

    
    func updateAnimationFrame() {
        if maxFrames <= 0 {
            maxFrames = Int(animationDuration / displayLink.duration);
        }
        
        let pCur = endpoints_scaled[_currentDigit];

        if currentFrame > maxFrames {
            currentFrame = 1;
            currentDigit = _nextDigit;
            displayLink?.paused = true;
            drawDigitWithoutAnimation(currentDigit);
        }
    }
