Fixed the lockscreen positon with a single notificaton

The notification was wrongly pushed up on the lockscreen
if there was only a single notification.

Test: Add a single notification, observe that it's not pushed in.
Bug: 32437839
Change-Id: Ica6275d0efb18a0a39d943e874d464a86593d5b3

packages/SystemUI/src/com/android/systemui/statusbar/stack/NotificationStackScrollLayout.java

@@ -769,11 +769,17 @@ public class NotificationStackScrollLayout extends ViewGroup
      *         Measured in absolute height.
      */
     private float getAppearEndPosition() {
-        int firstItemHeight = mTrackingHeadsUp || mHeadsUpManager.hasPinnedHeadsUp()
-                ? mHeadsUpManager.getTopHeadsUpPinnedHeight() + mBottomStackPeekSize
-                        + mBottomStackSlowDownHeight
-                : getFirstItemMinHeight() + mShelf.getIntrinsicHeight();
-        return firstItemHeight + (onKeyguard() ? mTopPadding : mIntrinsicPadding);
+        int appearPosition;
+        if (mTrackingHeadsUp || mHeadsUpManager.hasPinnedHeadsUp()) {
+            appearPosition = mHeadsUpManager.getTopHeadsUpPinnedHeight() + mBottomStackPeekSize
+                    + mBottomStackSlowDownHeight;
+        } else {
+            appearPosition = getFirstItemMinHeight();
+            if (mAmbientState.getShelfIndex() > 1) {
+                appearPosition += mShelf.getIntrinsicHeight();
+            }
+        }
+        return appearPosition + (onKeyguard() ? mTopPadding : mIntrinsicPadding);
     }
 
     /**