无法读取未定义的属性“ rotationOffset”

Question

我正在使用react-vr并尝试使用json对象来呈现图像，但是浏览器cannot read property 'rotationOffset' of undefined出现了错误。下面是我的代码供参考。

     static defaultProps = {
            portal: 'webTour.json',
          } //assigning the json to a variable.

        componentDidMount() {
        fetch(asset(this.props.portal).uri)
        .then(response => response.json())
        .then(responseData => {
          this.init(responseData);
        })
        .done
        ();
      }

    init(tourConfig) {
        // Initialize the tour based on data file.
        this.setState({
          data: tourConfig,
          locationId: null,
          nextLocationId: tourConfig.firstPhotoId,
          rotation: tourConfig.firstPhotoRotation + (tourConfig.photos[tourConfig.firstPhotoId].rotationOffset || 0),
        });
      }

render() {
//some code

const locationId = this.state.locationId;
    const photoData = (locationId && this.state.date.photos[locationId]) || null;
    const rotation = this.state.data.firstPhotoRotation + ((photoData && photoData.rotationOffset) || 0);
    const isLoading = this.state.nextLocationId !== this.state.locationId;

return (
<Pano source = {asset(this.state.data.photos[this.state.nextLocationID].uri)} />

}

以下是我的json文件供参考。

{
  "nave_icon": "gateway.png",
  "firstPhotoID" : "112001",
  "firstPhotoRotation" : 90,
  "photos":{
    "112001":{
      "rotationOffset": 0,
      "uri": "CustomPano_2.jpg",
}
}
}

我想做的是用Pano内部的对象更改背景图像。我是否缺少任何基本语法？我花了几个小时才发现问题不起作用。任何帮助深表感谢。