iOS My ios app rebooting the system ios 7

- (void)undo
{
    
        if(!_layersArray || _layersArray.count == 0)
            return;

        CAShapeLayer *lastLayer = [_layersArray lastObject];
        [lastLayer removeFromSuperlayer];
        [_layersArray removeLastObject];

    }
  


}

-(void)selectWidth:(int)tag
{
    self.width = tag;
}

-(void)selectColor:(int)tag
{
    if(tag == 0){
        self.color = [UIColor colorWithRed:235.0/255.0 green:235.0/255.0 blue:240.0/255.0 alpha:1];
    }else if(tag == 1){
        self.color = [UIColor colorWithRed:37.0/255.0 green:37.0/255.0 blue:41.0/255.0 alpha:1];
    }

}
#pragma mark -
#pragma mark Factory

- (void) createNewLayerAndPath
{
    _drawingLayer = [CAShapeLayer layer];
    _drawingLayer.strokeColor = self.color.CGColor;
    _drawingLayer.fillColor = [UIColor clearColor].CGColor;
    _drawingLayer.lineWidth = self.width;
    _drawingLayer.lineJoin = kCALineJoinRound;
    _drawingLayer.lineCap = kCALineCapRound;
    [self.layer addSublayer:_drawingLayer];
    _drawingPath = CGPathCreateMutable();
    [_layersArray addObject:_drawingLayer];
}

#pragma mark -
#pragma mark Calculation Of Middle Points

CGPoint midPoint(CGPoint p1 , CGPoint p2){

    return CGPointMake((p1.x + p2.x)*0.5, (p1.y + p2.y)*0.5);
}

#pragma mark -
#pragma mark Touches

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    if (self.delegate && [self.delegate respondsToSelector:@selector(viewTouched)]){
        [self.delegate viewTouched];
    }
    [self createNewLayerAndPath];
    UITouch *touch = [touches anyObject];
    CGPoint firstPoint = [touch locationInView:self];
    CGPathMoveToPoint(_drawingPath, NULL, firstPoint.x, firstPoint.y);

}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [touches anyObject];

    _currentPoint = [touch locationInView:self];
    _previousPoint = [touch previousLocationInView:self];

    CGPoint midpoint2 = midPoint(_currentPoint, _previousPoint);
    CGPathAddQuadCurveToPoint(_drawingPath, nil, _previousPoint.x, _previousPoint.y, midpoint2.x, midpoint2.y);
    [_drawingLayer setPath:NULL];
    [_drawingLayer setPath:_drawingPath];
}


- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [touches anyObject];
    _currentPoint = [touch locationInView:self];
    _previousPoint = [touch previousLocationInView:self];

    CGPoint midpoint2 = midPoint(_currentPoint, _previousPoint);

    CGPathAddQuadCurveToPoint(_drawingPath, nil, _previousPoint.x, _previousPoint.y, midpoint2.x, midpoint2.y);
    [_drawingLayer setPath:NULL];
    [_drawingLayer setPath:_drawingPath];


    if(_drawingPath != NULL)
        CGPathRelease(_drawingPath);
    _drawingLayer = nil;
}