Don't let two closing animations run at the same time

Fixes a flash when clicking on a single notification.

Bug: 17450892
Change-Id: Ia99c21a0bb30ce100532cfab66c96ec24f2412bf

packages/SystemUI/src/com/android/systemui/statusbar/phone/PanelView.java

@@ -684,7 +684,7 @@ public abstract class PanelView extends FrameLayout {
                 removeCallbacks(mPeekRunnable);
                 mPeekRunnable.run();
             }
-        } else if (!isFullyCollapsed() && !mTracking) {
+        } else if (!isFullyCollapsed() && !mTracking && !mClosing) {
             if (mHeightAnimator != null) {
                 mHeightAnimator.cancel();
             }