Fix NPE when closing folder.

There is a race condition where Folder is closing, it unbinds, and then
another call to AbstractFloatingView.closeAllOpenViews tries to close the
Folder again. But since the contents are unbound and removed from the folder,
it produces a NPE.

Bug: 153625271
Change-Id: Ia6c55f15cf7517e26af8f499bc0c1a4828737480

src/com/android/launcher3/folder/Folder.java

@@ -164,6 +164,7 @@ public class Folder extends AbstractFloatingView implements ClipPathView, DragSo
     @Thunk final ArrayList<View> mItemsInReadingOrder = new ArrayList<View>();
 
     private AnimatorSet mCurrentAnimator;
+    private boolean mIsAnimatingClosed = false;
 
     protected final Launcher mLauncher;
     protected DragController mDragController;
@@ -729,15 +730,24 @@ public class Folder extends AbstractFloatingView implements ClipPathView, DragSo
     }
 
     private void animateClosed() {
+        if (mIsAnimatingClosed) {
+            return;
+        }
         if (mCurrentAnimator != null && mCurrentAnimator.isRunning()) {
             mCurrentAnimator.cancel();
         }
         AnimatorSet a = new FolderAnimationManager(this, false /* isOpening */).getAnimator();
         a.addListener(new AnimatorListenerAdapter() {
+            @Override
+            public void onAnimationStart(Animator animation) {
+                mIsAnimatingClosed = true;
+            }
+
             @Override
             public void onAnimationEnd(Animator animation) {
                 closeComplete(true);
                 announceAccessibilityChanges();
+                mIsAnimatingClosed = false;
             }
         });
         startAnimation(a);