Google maps Googlemaps V3-可拖动多边形错误

下面是取自GoogleMapAPIv3文档的标准代码。如果将多边形选项设置为“可编辑”和“可拖动”，则当您将鼠标悬停/单击多边形的顶点时，会出现以下错误：

未捕获的TypeError:无法读取null的属性“\uuuue3”

错误是不一致的，因为它是临时出现的

  function initMap() {
        var map = new google.maps.Map(document.getElementById('map'), {
            center: { lat: -34.397, lng: 150.644 },
            zoom: 8
        });

        var drawingManager = new google.maps.drawing.DrawingManager({
            drawingMode: google.maps.drawing.OverlayType.POLYGON,
            drawingControl: false,
            drawingControlOptions: {
                position: google.maps.ControlPosition.TOP_CENTER,
                drawingModes: ['marker', 'circle', 'polygon', 'polyline', 'rectangle']
            },
            markerOptions: { icon: 'https://developers.google.com/maps/documentation/javascript/examples/full/images/beachflag.png' },
            polygonOptions: {
                fillColor: '#ffff00',
                fillOpacity: 1,
                strokeWeight: 5,
                clickable: true,
                editable: true,
                draggable:true,
                zIndex: 1
            }
        });
        drawingManager.setMap(map);

        google.maps.event.addListener(drawingManager, 'overlaycomplete', function (event) {

            drawingManager.setDrawingMode(null);
        });

    }

          initMap();

这是api中的错误吗？ 如果您对此事有任何意见，我们将不胜感激。 非常感谢