Fix bug #15729260 Switch should not have any outer glow ripple around its circle

- @null for the background

Change-Id: If2fa9f3dcdbd79af42e308120ce0c3ba3bc78ea3
diff --git a/res/layout/switch_bar.xml b/res/layout/switch_bar.xml
index cdf14d7..be24ff1 100644
--- a/res/layout/switch_bar.xml
+++ b/res/layout/switch_bar.xml
@@ -32,6 +32,7 @@
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:layout_gravity="center_vertical"
-            android:layout_marginEnd="?attr/switchBarMarginEnd" />
+            android:layout_marginEnd="?attr/switchBarMarginEnd"
+            android:background="@null" />
 </merge>