Add null check for empty recents view

Bug: 77533523
Change-Id: I8ba58d3ed35212b6c06e689281cb25b55ac79ae2
diff --git a/quickstep/src/com/android/quickstep/views/RecentsView.java b/quickstep/src/com/android/quickstep/views/RecentsView.java
index d95619c..b2bf030 100644
--- a/quickstep/src/com/android/quickstep/views/RecentsView.java
+++ b/quickstep/src/com/android/quickstep/views/RecentsView.java
@@ -1064,7 +1064,10 @@
     @Override
     protected void notifyPageSwitchListener(int prevPage) {
         super.notifyPageSwitchListener(prevPage);
-        getChildAt(mCurrentPage).sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_FOCUSED);
+        View currChild = getChildAt(mCurrentPage);
+        if (currChild != null) {
+            currChild.sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_FOCUSED);
+        }
     }
 
     @Override