Missing arrows

Hint:

`Konva warning: "points" attribute has non numeric element [object Object]. Make sure that all elements are numbers. 
    in StageWrap (created by Anonymous)
    in Anonymous (created by Edges)
    in Edges (created by NetworkVisualizer)
    in NetworkVisualizer (created by App)
    in App `

Sandbox:
https://codesandbox.io/s/objective-rain-iclcv8