Fix crash when toggling "Everything is awesome" in Stock's Settings.

sky/sdk/lib/widgets/material.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 import '../animation/animation_performance.dart';
 import '../painting/box_painter.dart';
 import 'animated_component.dart';
 import 'animated_container.dart';
 import 'basic.dart';
 import 'default_text_style.dart';
@@ skipping 16 matching lines @@
   Material({
     String key,
     this.child,
     MaterialType type: MaterialType.card,
     int level: 0,
     Color color: null
   }) : super(key: key) {
     if (level == null) level = 0;
     _container = new AnimatedContainer()
       ..shadow = new AnimatedType<double>(level.toDouble())
-      ..backgroundColor = new AnimatedColor(_getBackgroundColor(type, color))
+      ..backgroundColor = _getBackgroundColor(type, color)
       ..borderRadius = edges[type]
       ..shape = type == MaterialType.circle ? Shape.circle : Shape.rectangle;
     watchPerformance(_container.createPerformance(
         _container.shadow, duration: _kAnimateShadowDuration));
     watchPerformance(_container.createPerformance(
         _container.backgroundColor, duration: _kAnimateColorDuration));
   }
 
   Widget child;
 
   AnimatedContainer _container;
 
   void syncFields(Material source) {
     child = source.child;
     _container.syncFields(source._container);
     super.syncFields(source);
   }
 
-  Color _getBackgroundColor(MaterialType type, Color color) {
-    if (color != null)
-      return color;
-    switch (type) {
-      case MaterialType.canvas:
-        return Theme.of(this).canvasColor;
-      case MaterialType.card:
-        return Theme.of(this).cardColor;
-      default:
-        return null;
+  AnimatedColor _getBackgroundColor(MaterialType type, Color color) {
+    if (color == null) {
+      switch (type) {
+        case MaterialType.canvas: color = Theme.of(this).canvasColor; break;
+        case MaterialType.card: color = Theme.of(this).cardColor; break;
+      }
     }
+    return color == null ? null : new AnimatedColor(color);
   }
 
   Widget build() {
     return _container.build(
         new DefaultTextStyle(style: Theme.of(this).text.body1, child: child)
     );
   }
 
 }