Fix IndexOutOfBoundsException while handle app crash

The `mActivities` size could change while the the activity is
detached (r.detachFromProcess).

Bug: 274859740
Test: wm presubmit
Change-Id: I05d7b5a79d3f7cffca707a7ad7cce1b871f0c8ff

services/core/java/com/android/server/wm/WindowProcessController.java

@@ -378,8 +378,9 @@ public class WindowProcessController extends ConfigurationContainer<Configuratio
     }
 
     void handleAppCrash() {
-        for (int i = mActivities.size() - 1; i >= 0; --i) {
-            final ActivityRecord r = mActivities.get(i);
+        ArrayList<ActivityRecord> activities = new ArrayList<>(mActivities);
+        for (int i = activities.size() - 1; i >= 0; --i) {
+            final ActivityRecord r = activities.get(i);
             Slog.w(TAG, "  Force finishing activity "
                     + r.mActivityComponent.flattenToShortString());
             r.detachFromProcess();