我尝试创建一个由4个对象组成的JSON字符串，并将其从C#控制器发送到Axios的React函数，然后将数据放入div的类名中，以便根据它们是否处于活动状态来更改它们的样式。使用我的代码时，我遇到了UncaughtTypeError：无法读取null的属性（阅读“0”）。我认为数据没有到达函数，但我不确定原因。代码如下：
js（我尝试在其中设置类名的值）

import React, { useState, useEffect } from 'react';
import axios from "axios";

function ServerStatuses() {
    const [serverCycleData, setServerCycleData] = useState(null);

    useEffect(() => {
        //sets the interval for the serverCycle data to be sent over every 2 seconds
        const serverCycleData = () => {
            axios.get("/serverCycle")
                .then(res => {
                    setServerCycleData(res.data);
                })
        }
        serverCycleData();
        const interval = setInterval(() => {
            serverCycleData()
        }, 50000);
        return () => clearInterval(interval);
    }, []);

        return (
            <div id="statuses">
                <div id="LWStatus" className={serverCycleData[0].className}>SERVER</div>
                <div id="CONAStatus" class={serverCycleData[1].className}>CONA</div>
                <div id="PDAStatus" class={serverCycleData[2].className}>PDA</div>
                <div id="OverallStatus" class={serverCycleData[3].className}>ERROR</div>
            </div>
        )
    };

export default ServerStatuses;

cs（第一个是我的API调用）

[HttpGet]
        [Route("/hGrabLocation")]
        public string GrabLocation()
        {
            var plantLocation = "LOCATION HERE";
            //using the object here to pull the data
            if (ObjSiteConfiguration.Initialized)
            {
                plantLocation = ObjSiteConfiguration.Palletizers[0].PlantName;
            }
            else
            {
                plantLocation = "Site not initialized";
            }

            return plantLocation;

        }

ProductionController.cs（这只是我在开始时创建的列表，用于在中存储和提取值）

private List<ObjServerStatus> serverStatuses = new()
        {
                new ObjServerStatus{serverType = "LW", serverStatus = false, statusClass = "header-icon_error"},
                new ObjServerStatus{serverType = "CONA", serverStatus = false, statusClass = "header-icon_error"},
                new ObjServerStatus{serverType = "PDA", serverStatus = false, statusClass = "header-icon_error"},
                new ObjServerStatus{serverType = "OVERALL", serverStatus = false, statusClass = "header-icon_error"}
            };

我试图运行该网站，并不断得到一个未捕获的TypeError：无法读取null的属性（阅读“0”）。我希望加载标头，并且div标记将加载并附加正确的类。