Avoid stroke around shape during morphing animation

[zapletnev]

import Foundation
import Macaw

class MorhView: MacawView {
    required convenience init?(coder aDecoder: NSCoder) {
        let circle = Shape(
            form: Circle(r: 15.0),
            fill: Color.silver
        )
        
        let node = Group(contents: [circle])
        node.place = node.place.move(dx: 200, dy: 200)
        
        node.onTouchPressed { f in
            circle.fillVar.animate(to: Color.white, during: 2.0)
        }
        self.init(node: node, coder: aDecoder)
    }
}