When using the smooth operator, the thickness would not be
smoothed on the first iteration. This was becasue the inner loop
was set to run r * 20 times but r starts at 0.

The fix makes sure that "Smooth Thickness" works on the first
iteration by using a fixed value of 20 as the loop limit. This
makes sure that for every iteration, we run the smoothing of the
thickness 20 more times.