function errorHandler(errorMessage) {
    //curisosity, check out the error in the console
    console.log(errorMessage);

    //simply remove the error, the user never see it
    google.visualization.errors.removeError(errorMessage.id);
}

function drawChart(json) {
    var data = new google.visualization.DataTable(json); //here, JSON is buggy
    var options = {
      title: 'test'
    };
    var chart = new google.visualization.LineChart(document.getElementById('chart_div'));

    //attach the error handler here, before draw()
    google.visualization.events.addListener(chart, 'error', errorHandler);

    chart.draw(data, options);
}

var data = google.visualization.arrayToDataTable(sourcedata);