Fix panel height when only one notification is shown

Also fix the place holder height for the stack when QS is expanded.

Change-Id: Ia28373c21b5d2155e735425d5657dde2dec49c6d
diff --git a/packages/SystemUI/res/values/dimens.xml b/packages/SystemUI/res/values/dimens.xml
index 5400326..e20947f 100644
--- a/packages/SystemUI/res/values/dimens.xml
+++ b/packages/SystemUI/res/values/dimens.xml
@@ -232,8 +232,9 @@
     <!-- Space reserved for the cards behind the top card in the bottom stack -->
     <dimen name="bottom_stack_peek_amount">12dp</dimen>
 
-    <!-- bottom_stack_peek_amount + notification_min_height -->
-    <dimen name="min_stack_height">76dp</dimen>
+    <!-- bottom_stack_peek_amount + notification_min_height
+         + notification_collapse_second_card_padding -->
+    <dimen name="min_stack_height">84dp</dimen>
 
     <!-- The height of the area before the bottom stack in which the notifications slow down -->
     <dimen name="bottom_stack_slow_down_length">12dp</dimen>