Fix visibility of notification footer divider

Now it is only visible when the notification footer is present,
instead of always being visible.

Change-Id: Ie85ff31918901115cdfe55b36e75aa80b43e7b13
diff --git a/res/layout/notification.xml b/res/layout/notification.xml
index a03dd08..a183c92 100644
--- a/res/layout/notification.xml
+++ b/res/layout/notification.xml
@@ -66,7 +66,8 @@
             android:layout_width="match_parent"
             android:layout_height="@dimen/popup_item_divider_height"
             android:background="?android:attr/listDivider"
-            android:layout_below="@id/main_view"/>
+            android:layout_below="@id/main_view"
+            android:visibility="gone" />
 
         <include layout="@layout/notification_footer"
             android:id="@+id/footer"