Work around a crash in UITableView when changing layout during scrolling

SomeUITableViewCell.m

-(void)triggerRelayoutIfNecessary
{
    [_activityIndicator stopAnimating];

    float newHeight = [self.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize].height;
    if ( newHeight != _lastHeight )
    {
        UITableView* tv = (UITableView*)[self LT_findFirstSuperviewOfClass:UITableView.class];
        if ( tv.isDragging || tv.isDecelerating )
        {
            LOG( @"Can't trigger updating because tableview is being scrolled" );
            dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.1 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
                [self triggerRelayoutIfNecessary];
            });
            return;
        }
        _lastHeight = newHeight;
        [self setNeedsUpdateConstraints];

        [tv beginUpdates];
        [tv endUpdates];
    }
}