错误：无效的LatLng对象：54，未定义

如何解决错误：无效的LatLng对象：54，未定义

我正在研究react，并且我是一个初学者，我正在尝试使用React的Leaflet工具制作地图。事实是，当我选择一个特定的国家/地区时，我希望它转到所选的国家/地区，但会生成错误“错误：无效的LatLng对象：（54，未定义）”，如果您能给我一个解决问题的方法我有点复杂，非常感谢。

import { MenuItem,FormControl,Select,Card,CardContent} from '@material-ui/core';
import React,{useState,useEffect} from 'react';
import './App.css';
import InfoBox from './InfoBox';
import Map from './Map';
import Table from "./Table";
import { sortData } from "./util";
import LineGraph from "./LineGraph";
import "leaflet/dist/leaflet.css";

function App() {
  const [countries,setCountries] = useState([]);
  const [country,setCountry] = useState('worldwide');
  const [countryInfo,setCountryInfo] = useState({});
  const [tableData,setTableData] = useState([]);
  const [mapCenter,setMapCenter] = useState({ lat: 34.80746,lng: -40.4796});
  const [mapZoom,setMapZoom] = useState(3);
  const [mapCountries,setMapCountries] = useState([]);

  useEffect(() => {

    fetch("https://disease.sh/v3/covid-19/all").then((response) => response.json()).then(data => {
      setCountryInfo(data);
    });
  },[]);

  useEffect(() => {
    const getCountriesData = async () => {
      await fetch("https://disease.sh/v3/covid-19/countries").then((response) => response.json()).then((data) => {

        const countries = data.map((country) => ( //ciudades por la API
          {
            name: country.country,// United States,United Kingdom
            value: country.countryInfo.iso2 // UK,USA,FR
          }
        ));
        
        const sortedData = sortData(data);
        setTableData(sortedData);
        setMapCountries(data);
        setCountries(countries); //Cambio de estado por las ciudades de las api 
      });
    };

    getCountriesData();
  },[]);

  const onCountryChange = async (event) => {
    const countryCode = event.target.value;
    setCountry(countryCode);

    const url = countryCode === "worldwide" ? 'https://disease.sh/v3/covid-19/all' : `https://disease.sh/v3/covid-19/countries/${countryCode}`;

    await fetch(url).then((response) => response.json()).then((data) => {
      
      setCountry(countryCode);
      setCountryInfo(data);  
      
      setMapCenter([data.countryInfo.lat,data.countryInfo.lng]);
      setMapZoom(4);
    });
  };
 
  return (
    <div className="app">
      <div className="app__left">
        <div className="app__header">
          <h1>COVID 19 TRACKER</h1>
          <FormControl className="app__dropdown">
            <Select variant="outlined" onChange={onCountryChange} value={country}>
              <MenuItem value="worldwide">Worldwide</MenuItem>
              {countries.map((country) => (
                  <MenuItem value={country.value}>{country.name}</MenuItem>
                ))}
            </Select>
          </FormControl>
        </div>
        
        <div className="app__stats">
          <InfoBox 
          title="Coronavirus Cases" 
          cases={countryInfo.todayCases} 
          total={countryInfo.cases}
          />

          <InfoBox 
          title="Recovered" 
          cases={countryInfo.todayRecovered} 
          total={countryInfo.recovered}
          />

          <InfoBox 
          title="Deaths" 
          cases={countryInfo.todayDeaths} 
          total={countryInfo.deaths}
          />

        </div>

        <Map center={mapCenter} zoom={mapZoom} countries={mapCountries}/>

      </div>
      <Card className="app__right">
        <CardContent>
          <h3>Live cases by country</h3>
          <Table countries={tableData}/>
          <h3>Worldwide new cases</h3>
          <LineGraph/>
        </CardContent>
      </Card>
    </div>
  );
};

export default App;

接下来我将显示Map的js文件

import React from 'react';
import './Map.css';
import { Map as LeafletMap,TileLayer } from "react-leaflet";

function Map({countries,center,zoom}) {
    return (
        <div className="map">
            <LeafletMap center={center} zoom={zoom}>
                <TileLayer
                    url="https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png"
                    attribution='&copy; <a href="https://www.openstreetmap.org/copyright">OpenStreetMap</a> contributors'
                />
            </LeafletMap>
        </div>
    );
}

export default Map;