Truthy / Falsy check breaks for a cubic bezier with the final point's x or y value being 0

[Rheeseyb]

Inside function function Bezier(ax, ay, bx, by, cx, cy, dx, dy) there is the following check:
if(dx && dy) {
From my understanding, this was included so that the function could be used for quadratic curves (i.e. the "Q" and "q" commands), but results in undesired behaviour if specifying a cubic bezier with a zero for either of those values