rem: if (i == 0)
add: if (i <= 0)
context: void gnibbles_worm_undraw_nth (GnibblesWorm *worm, gint offset){	int x, y, i, j;	x = worm->xhead;	y = worm->yhead;	i = worm->start - 1;	if (i == 0)		i = CAPACITY - 1;	for (j = 0; j < offset; j++) {		if ((worm->stop == 0 && i == CAPACITY - 1) ||				(worm->stop != 0 &&				 i == worm->stop - 1))			return;		x += worm->xoff[i];		y += worm->yoff[i];		i--;		if (i == 0)			i = CAPACITY - 1;	}	while (1) {		gnibbles_draw_pixmap (BLANKPIXMAP, x, y);		for (j = 0; j < ERASESIZE; j++) {			x += worm->xoff[i];			y += worm->yoff[i];			if ((worm->stop == 0 && i == CAPACITY - 1) ||					(worm->stop != 0 &&					 i == worm->stop - 1))				return;			i--;			if (i == 0)				i = CAPACITY - 1;		}	}}