Fix NPE when logging already removed pip activity

Bug: 148943800
Test: Manual
diff --git a/packages/SystemUI/src/com/android/systemui/pip/phone/PipManager.java b/packages/SystemUI/src/com/android/systemui/pip/phone/PipManager.java
index 1fdf92e..32e9a03 100644
--- a/packages/SystemUI/src/com/android/systemui/pip/phone/PipManager.java
+++ b/packages/SystemUI/src/com/android/systemui/pip/phone/PipManager.java
@@ -115,7 +115,7 @@
 
         @Override
         public void onActivityUnpinned() {
-            final Pair<ComponentName, Integer> topPipActivityInfo = PipUtils.getTopPinnedActivity(
+            final Pair<ComponentName, Integer> topPipActivityInfo = PipUtils.getTopPipActivity(
                     mContext, mActivityManager);
             final ComponentName topActivity = topPipActivityInfo.first;
             mMenuController.onActivityUnpinned();