am creating a d3.js and react pie chart and the path element is giving an error on the d attribute expecting a number.

Error: attribute d: Expected number, "MNaN,NaNLNaN,NaNZ".

am looking at my code and I can't figure out the problem.

```
import React from 'react'
import * as d3 from 'd3'

function Pie() {

    const data = [{name: 'simba', value: 60}, {name: 'kiki', value: 40}]
    const pieData = d3.pie().value(d => d.value)(data)

    const arc = d3.arc()
        .innerRadius(0)
        .outerRadius(50)

    return (
        <svg>
            <g transform={`translate(50, 50)`} >
                <path d={arc(pieData)}/>
            </g>  
        </svg>
    )
}

export default Pie 

```