don't call the reparent method when the old parent of task is removed.

 The activities in the task may already be finishing. Then the task could be removed when performing the idle check.

Test: monkey test
Flag: EXEMPT bugfix
Bug: 388883786
Change-Id: I762d3aaaa7a4b2eac2784d1f578960c4348a5a9d
1 file changed