树形图收缩后消失echarts tree配置项内容和展示

树形图开启平移和缩放，并用鼠标滚轮缩放后，再收缩根节点，此时整个图形都不见了

      option = {
    tooltip: {
        trigger: 'item',
        triggerOn: 'mousemove'
    },
    series: [{
        name: "我的图形",
        type: 'tree',
        data: [{
            "name": "我的图形",
            "value": 44,
            "children": [{
                "name": "二级1",
                "value": 45,
                "children": [{
                    "name": "三级1",
                    "value": 48
                }]
            }, {
                "name": "二级2",
                "value": 46,
                "children": [{
                    "name": "三级2",
                    "value": 49
                }, {
                    "name": "三级3",
                    "value": 50
                }]
            }, {
                "name": "二级3",
                "value": 47,
                "children": [{
                    "name": "三级4",
                    "value": 51
                }]
            }]
        }],
        layout: "orthogonal",
        orient: "horizontal",
        roam: true,
        symbol: 'circle',
        symbolSize: [50, 20],
        lineStyle: {
            color: "#CCC",
            width: 1.5,
            curveness: 0.5
        },
        itemStyle: {
            borderColor: "#c23531",
            borderWidth: 0.0,
            borderType: 'solid',
            color: ""
        },
        label: {
            color: "#333",
            fontSize: 12
        }
    }]
};