arc() does infinite loop on NaN or inf

[Swrup]

Hello,

If start_angle or sweep_angle are NaN or inf, arc() will make stroke() fall into an infinite loop.
Maybe arc() should panic instead?

[jrmuizel]

What was the situation where you ran into this?

[Swrup]

Here is the code
Notice that in StrokeStyle dash_offset was set to 1.
It seems it only happens if I change the StrokeStyle.

use raqote::*;

fn main() {
    let mut dt = DrawTarget::new(400, 400);

    let mut pb = PathBuilder::new();
    pb.arc(100., 100., 10., 1. / 0., 2.);
    let path = pb.finish();

    dt.stroke(
        &path,
        &Source::Solid(SolidSource {
            r: 0x0,
            g: 0x0,
            b: 0x80,
            a: 0x80,
        }),
        &StrokeStyle {
            cap: LineCap::Round,
            join: LineJoin::Round,
            width: 10.,
            miter_limit: 2.,
            dash_array: vec![10., 18.],
            dash_offset: 1.,
        },
        &DrawOptions::new(),
    );

    println!("{:?}", dt.write_png("example.png"));
}