Fix analyzer warning

sky/sdk/lib/widgets/material.dart

Index: sky/sdk/lib/widgets/material.dart
diff --git a/sky/sdk/lib/widgets/material.dart b/sky/sdk/lib/widgets/material.dart
index f4254736b0c2f1ec4a246f80f2455a675a8ad119..cb24a8dd0a81fe1deba064097e92b5f5e3fea8f7 100644
--- a/sky/sdk/lib/widgets/material.dart
+++ b/sky/sdk/lib/widgets/material.dart
@@ -56,8 +56,14 @@ class Material extends AnimatedComponent {
   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;
+        case MaterialType.canvas:
+          color = Theme.of(this).canvasColor;
+          break;
+        case MaterialType.card:
+          color = Theme.of(this).cardColor;
+          break;
+        default:
+          break;
       }
     }
     return color == null ? null : new AnimatedColor(color);