donut chart data.empty.label.text is overlaped on title.

[koocci]

Hello,
When I use donut chart, data.empty.label.text is overlaped on donut.title.
I think title have to disappear when data is empty.
Can you please support above issue?
thanks.

var chart = c3.generate({
    data: {
        columns: [
            ['data1', 30],
            ['data2', 120],
        ],
        type : 'donut',
        empty : {
            label: {
                text: "No Data"
            }
        }
    },
    donut: {
        title: "Iris Petal Width"
    }
});

• C3 version: 0.7.10
• D3 version: v5.16.0
• Browser: chrome, explorer
• OS: MacOS, Window10