Exporting with image problem

by Black Label

HTML

<script src="https://code.highcharts.com/gantt/highcharts-gantt.js"></script>
<script src="https://code.highcharts.com/gantt/modules/exporting.js"></script>

<div id="container"></div>

CSS

#container, #button-container {
    max-width: 800px;
    margin: 1em auto;
}

JavaScript

Highcharts.ganttChart('container', {

    title: {
        text: 'Highcharts Gantt Chart'
    },

    subtitle: {
        text: 'With custom symbols in data labels'
    },

    xAxis: {
        minPadding: 0.05,
        maxPadding: 0.05
    },

    yAxis: {
        categories: ['Prototyping', 'Development', 'Testing']
    },

    tooltip: {
        outside: true
    },

    series: [{
        name: 'Project 1',
        data: [{
            start: Date.UTC(2018, 11, 1),
            end: Date.UTC(2018, 11, 2),
            y: 0,
            assignee: 'JonArild'
        }, {
            start: Date.UTC(2018, 11, 2),
            end: Date.UTC(2018, 11, 5),
            y: 1,
            assignee: 'Oystein',
            fontSymbol: 'exclamation'
        }, {
            start: Date.UTC(2018, 11, 8),
            end: Date.UTC(2018, 11, 9),
            y: 2,
            assignee: 'Torstein'
        }, {
            start: Date.UTC(2018, 11, 9),
            end: Date.UTC(2018, 11, 19),
            y: 1,
            assignee: 'JonArild'
        }, {
            start: Date.UTC(2018, 11, 10),
            end: Date.UTC(2018, 11, 23),
            y: 2,
            assignee: 'Torstein',
            fontSymbol: 'smile-o'
        }],
        dataLabels: [{
            enabled: true,
            format: '<div style="width: 20px; height: 20px; overflow: hidden; border-radius: 50%; margin-left: -25px">' +
                '<img src="https://www.highcharts.com/images/employees2014/{point.assignee}.jpg" ' +
                'style="width: 30px; margin-left: -5px; margin-top: -2px"></div>',
            useHTML: true,
            align: 'left'
        }, {
            enabled: true,
            format: '<i class="fa fa-{point.fontSymbol}" style="font-size: 1.5em"></i>',
            useHTML: true,
            align: 'right'
        }]
    }],
		exporting: {
			allowHTML: true
		}
});