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diff --git a/dygraph-layout.js b/dygraph-layout.js
index 8147e48..58f169b 100644 (file)
--- a/dygraph-layout.js
+++ b/dygraph-layout.js
@@ -361,6 +361,7 @@ DygraphLayout.prototype.removeAllDatasets = function() {
  */
 DygraphLayout.prototype.unstackPointAtIndex = function(idx) {
   var point = this.points[idx];
+  // If the point is missing, no unstacking is necessary
   if (!point.yval) {
     return point;
   }