Index: node_modules/d3-selection/src/selection/node.js
===================================================================
--- node_modules/d3-selection/src/selection/node.js	(revision e4c61dd6cd86e06265bc2bd91adba84a0f04044a)
+++ node_modules/d3-selection/src/selection/node.js	(revision e4c61dd6cd86e06265bc2bd91adba84a0f04044a)
@@ -0,0 +1,11 @@
+export default function() {
+
+  for (var groups = this._groups, j = 0, m = groups.length; j < m; ++j) {
+    for (var group = groups[j], i = 0, n = group.length; i < n; ++i) {
+      var node = group[i];
+      if (node) return node;
+    }
+  }
+
+  return null;
+}