Logging Arrows without radius doesn't show anything

[Wumpf]

Minimal repro:

fn run(mut session: rerun::Session) -> Result<(), rerun::MsgSenderError> {
    rerun::MsgSender::new("my_points")
        .with_component(&[rerun::components::Arrow3D {
            origin: rerun::components::Vec3D::new(0.0, 0.0, 0.0),
            vector: rerun::components::Vec3D::new(0.0, 10.0, 1.0),
        }])?
        .send(&mut session)
}

fn main() {
    let session = rerun::Session::init("arrow", true);
    session.spawn(run).unwrap();
}

Need to add .with_component(&[rerun::components::Radius(1.0)])? to see anything. Also happens in python!

Had a brief look in our code: I think the problem is that LineStripFlags::get_triangle_cap_tip_length doesn't deal with auto size correctly, but haven't given it much thought. In any case the issue is bound to be in Arrows3DPart