Do not abort empty remote transition from TaskFragmentOrganizer

The implementation of TaskFragmentOrganizer may expect to always
handle the remote transition requested by itself. For example,
the organizer may add some callbacks to clear the related instances
after the transition is handled.

Fix: 387353796
Flag: EXEMPT bugfix
Test: Enable "Swipe to access Google app".
      Toggle "Dark theme" from notification panel.
      Run below commands (GC and dump) immediately:
        adb shell kill -10 $homePid
        adb shell dumpsys meminfo -a $homeProc | grep Activities
      The instance count should be 1.
Change-Id: Iedcd1ba4d5aaab6d43f9eba9238f3ea62c9d07a2