message: fix: the cubic tangent at
diff: @@ -31,7 +31,7 @@ export class BezierCurveShape {
  function someVectorAt(shape: BezierCurveShape, t: number, isTangent: boolean) {
  const cpx2 = shape.cpx2;
  const cpy2 = shape.cpy2;
  - if (cpx2 === null || cpy2 === null) {
  + if (cpx2 != null || cpy2 != null) {
  return [
  (isTangent ? cubicDerivativeAt : cubicAt)(shape.x1, shape.cpx1, shape.cpx2, shape.x2, t),
  (isTangent ? cubicDerivativeAt : cubicAt)(shape.y1, shape.cpy1, shape.cpy2, shape.y2, t)
  