"undefined" show on top of tracker info

[nichliu]

"undefined" show on top of tracker info, how can I remove it

Also trackerShowTime=true is not working

Here is my code

<ChartRow
    height="400"
    trackerInfoValues={[
        {label: "Temperature", value: this.state.temperature.toString()+" °C"},
        {label: "Humidity", value: this.state.humidity.toString()+ " %RH"}
     ]}
    trackerInfoWidth={130}
    trackerInfoHeight={40}
    trackerTime={this.state.tracker}
    trackerShowTime={true}
 >