Ensure SAVE_APP_PAIR is only used for GroupedTaskView

- Check if TaskView is GroupedTaskView before casting to avoid a crash, caused by DesktopTaskView.containsMultipleTasks() is true but is not a GroupedTaskView

Fix: 331226084
Test: With Talkback on and Desktop task, go to Overview
Flag: ACONFIG com.android.window.flags.enable_desktop_windowing_mode DEVELOPMENT
Change-Id: Ic2f1b940bb5a6b0cf452465b9cc15ebf4c256858
diff --git a/quickstep/src/com/android/quickstep/TaskShortcutFactory.java b/quickstep/src/com/android/quickstep/TaskShortcutFactory.java
index c97e62a..7f1883d 100644
--- a/quickstep/src/com/android/quickstep/TaskShortcutFactory.java
+++ b/quickstep/src/com/android/quickstep/TaskShortcutFactory.java
@@ -332,11 +332,13 @@
             // - the task in question is a single task
             // - at least one app in app pair is unpinnable
             // - the Overview Actions Button should be visible
+            // - the task is not a GroupedTaskView
             if (!FeatureFlags.enableAppPairs()
                     || !recentsView.supportsAppPairs()
                     || !taskView.containsMultipleTasks()
                     || hasUnpinnableApp
-                    || shouldShowActionsButtonInstead) {
+                    || shouldShowActionsButtonInstead
+                    || !(taskView instanceof GroupedTaskView)) {
                 return null;
             }