Avoid undefined in textContent

src/standard/effects.html

@@ -201,6 +201,10 @@
         if (property === 'className') {
           value = this._scopeElementClass(node, value);
         }
+        // Some browsers serialize `undefined` textContent to `"undefined"`
+        if (property === 'textContent') {
+          value = value == undefined ? '' : value;
+        }
         return node[property] = value;
       }
     }

test/unit/bind-elements.html

@@ -16,7 +16,8 @@
     custom-event-object-value="{{customEventObject.value::change}}">
     Test
     </div>
-    <span id="{{boundId}}"></span>
+    <span id="boundText">{{text}}</span>
+    <span idtest id="{{boundId}}"></span>
 </template>
 <script>
   Polymer({

test/unit/bind.html

@@ -33,7 +33,28 @@
   });
 
   test('id is bindable', function() {
-    assert.equal(Polymer.dom(el.root).querySelector('span').id, 'span', 'id bound to <span> not found');
+    assert.equal(Polymer.dom(el.root).querySelector('span[idtest]').id, 'span', 'id bound to <span> not found');
+  });
+
+  test('textContent binding updates', function() {
+    el.text = 'this is a test';
+    assert.equal(el.$.boundText.textContent, 'this is a test', 'Value not propagated to textContent');
+  });
+
+  test('textContent binding to undefined is empty string', function() {
+    el.text = 'this is a test';
+    el.text = undefined;
+    assert.equal(el.$.boundText.textContent, '', 'undefined bound to textContent should be empty string');
+  });
+
+  test('textContent binding to null is empty string', function() {
+    el.text = null;
+    assert.equal(el.$.boundText.textContent, '', 'null bound to textContent should be empty string');
+  });
+
+  test('textContent binding to zero is empty correct', function() {
+    el.text = 0;
+    assert.equal(el.$.boundText.textContent, '0', 'zero bound to textContent should be empty string');
   });
 
   test('camel-case binding updates', function() {