Ensure points passed to convex polygon aren't empty

src/shape/convex_polygon.rs

@@ -32,6 +32,9 @@ impl ConvexPolygon {
     /// Convexity of the input polyline is not checked.
     /// Returns `None` if all points form an almost flat line.
     pub fn from_convex_polyline(mut points: Vec<Point<Real>>) -> Option<Self> {
+        if points.is_empty() {
+            return None;
+        }
         let eps = ComplexField::sqrt(crate::math::DEFAULT_EPSILON);
         let mut normals = Vec::with_capacity(points.len());
         // First, compute all normals.