Leaflet: Uncaught TypeError: Cannot read properties of null (reading '0')

Question

I am trying to display a polygon on the map that can be flexibly updated by a reload. To do this, I call the data as follows:

    $.get('./load-polygon.php', function(csvString) {
        
        map.eachLayer(function (layer)
        {
            if (layer instanceof L.Polygon)
            {
                layer.remove();
            }
        });
        
        var data = Papa.parse(csvString, {header: true, dynamicTyping: true}).data;
        
        for (var i in data)
        {
            var row = data[i];
            var polygon = L.polygon([row.Polygon], {color: '#ff4f00'}).addTo(map);
        }
    });

The data content of the load-polygon.php looks like this:

"Polygon" "[52.485774, 13.436072],[52.534669, 13.397620],[52.542187, 13.475554],[52.499153, 13.514693]"

If I output all data via the console and include the polygon manually, everything works without any problems.

Unfortunately, I get an error message and the polygon is not displayed.

Uncaught TypeError: Cannot read properties of null (reading '0')
    at i._projectLatlngs (leaflet.js:5:79693)
    at i._projectLatlngs (leaflet.js:5:79838)
    at i._projectLatlngs (leaflet.js:5:79838)
    at i._project (leaflet.js:5:79369)
    at i._reset (leaflet.js:5:75435)
    at i.onAdd (leaflet.js:5:74837)
    at i._layerAdd (leaflet.js:5:63932)
    at i.whenReady (leaflet.js:5:42041)
    at i.addLayer (leaflet.js:5:64307)
    at i.addTo (leaflet.js:5:63275)

If I output the data, everything looks fine.

console.log(row.Polygon);

Manually, the polygon can then be inserted with the appropriate values.

var latlngs = [[52.485774, 13.436072],[52.534669, 13.397620],[52.542187, 13.475554],[52.499153, 13.514693]];

var polygon = L.polygon(latlngs, {color: '#ff4f00'}).addTo(map);

Maybe someone recognizes my problem... Thanks in advance... And best regards.