Trail is broken without order encoding

[angiehjort]

const groupMap = this.marker.getTransformedDataMap("order.order");
const limits = {};
for (let key of markers.keys()) {
limits[key] = this.groupMapExtent(groupMap, key);
}

throws groupMap (undefined) is not iterable

yet, enabling order encoding results in chart not respecting splash load and waiting full data to render both splash and full picture