From 09bb6cd8799cd895694f5e3a913fbecc7e010388 Mon Sep 17 00:00:00 2001
From: Limon Monte <limon.monte@gmail.com>
Date: Mon, 18 Dec 2017 15:02:23 +0200
Subject: [PATCH] fix(FlattenedNodesObserver): do not fail on node without
 children

---
 lib/utils/flattened-nodes-observer.html |  4 ++--
 test/unit/flattened-nodes-observer.html | 10 ++++++++++
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/lib/utils/flattened-nodes-observer.html b/lib/utils/flattened-nodes-observer.html
index 78f74127c5..0a291ec248 100644
--- a/lib/utils/flattened-nodes-observer.html
+++ b/lib/utils/flattened-nodes-observer.html
@@ -130,7 +130,7 @@
     connect() {
       if (isSlot(this._target)) {
         this._listenSlots([this._target]);
-      } else {
+      } else if (this._target.children) {
         this._listenSlots(this._target.children);
         if (window.ShadyDOM) {
           this._shadyChildrenObserver =
@@ -159,7 +159,7 @@
     disconnect() {
       if (isSlot(this._target)) {
         this._unlistenSlots([this._target]);
-      } else {
+      } else if (this._target.children) {
         this._unlistenSlots(this._target.children);
         if (window.ShadyDOM && this._shadyChildrenObserver) {
           ShadyDOM.unobserveChildren(this._shadyChildrenObserver);
diff --git a/test/unit/flattened-nodes-observer.html b/test/unit/flattened-nodes-observer.html
index 27b0190d24..54cdd22604 100644
--- a/test/unit/flattened-nodes-observer.html
+++ b/test/unit/flattened-nodes-observer.html
@@ -1039,6 +1039,16 @@
       document.body.removeChild(host);
     });
 
+    test('should not fail on node without children', function() {
+      var recorded;
+      var el = document;
+      var observer = new Polymer.FlattenedNodesObserver(el, function(info) {
+        recorded = info;
+      });
+      assert.equal(recorded, null);
+      observer.disconnect();
+    });
+
   });
 
 </script>