Handle the case where launch root is not attached

- Throw illegalstateException if the task that is being set as launch
  root task is not attached to the wm hierarchy - in other words:
  when it doesn't have a display area.
- This makes sure that system server doesn't crash with NPE when this
  happens.

Bug: 283152174
Test: Tested manually using the car portrait target
Change-Id: I330560cbb1ecf8f267c37e1696084b6872c3068e

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

@@ -845,11 +845,14 @@ class WindowOrganizerController extends IWindowOrganizerController.Stub
             case HIERARCHY_OP_TYPE_SET_LAUNCH_ROOT: {
                 final WindowContainer wc = WindowContainer.fromBinder(hop.getContainer());
                 final Task task = wc != null ? wc.asTask() : null;
-                if (task != null) {
+                if (task == null) {
+                    throw new IllegalArgumentException("Cannot set non-task as launch root: " + wc);
+                } else if (task.getTaskDisplayArea() == null) {
+                    throw new IllegalArgumentException("Cannot set a task without display area as "
+                            + "launch root: " + wc);
+                } else {
                     task.getDisplayArea().setLaunchRootTask(task,
                             hop.getWindowingModes(), hop.getActivityTypes());
-                } else {
-                    throw new IllegalArgumentException("Cannot set non-task as launch root: " + wc);
                 }
                 break;
             }