Address a couple small followups for TaskbarInsetsController

- Added no-op onDestroy()
- Reformated some if conditions, also adding
  AbstractFloatingView.hasOpenView()

Test: TaplTestsTaskbar
Bug: 215411414
Change-Id: I89b39ca5fabd03f5ac0f25d6ef69170683cf060d

quickstep/src/com/android/launcher3/taskbar/TaskbarControllers.java

@@ -160,6 +160,7 @@ public class TaskbarControllers {
         taskbarForceVisibleImmersiveController.onDestroy();
         taskbarAllAppsController.onDestroy();
         navButtonController.onDestroy();
+        taskbarInsetsController.onDestroy();
 
         mControllersToLog = null;
     }