Show a warning toast if a task is not valid to bubble in onTaskInfoChanged.

Demo: http://screencast/cast/NjQ0MjkyOTY5MzM5Mjg5NnwzZjNlOWQzMy1jYg
Bug: 411558731
Bug: 419341634
Bug: 419379112
Test: wm presubmit
Flag: com.android.wm.shell.enable_create_any_bubble
Change-Id: I940d732658e0feeb71feeb7704d78b3efe0165cd