Actually you need to remove drilldown
attribute from the pie that has no link with donut pie and check the data with:
if(data[i].drilldown!=undefined){
for (var j = 0; j < data[i].drilldown.data.length; j++) {
var brightness = 0.2 - (j /data[i].drilldown.data.length) / 5 ;
versionsData.push({
name: data[i].drilldown.categories[j],
y: data[i].drilldown.data[j],
color: Highcharts.Color(data[i].color).brighten(brightness).get()
});
}
}}
or put empty drilldown like this Demo