UX: If a user cancels system dialog for bulk export modal doesn't close

[ermbutler]

As part of recent work for bulk downloads was made idempotent with the filesystem access API, which also generates this system dialog for users in some cases. This is expected behavior, and once accepted it doesn't impact the process. But if I user decides to cancel at this point, the modal behind it is stuck open, and should also close/Cacnel to reflect the state of the system (nothing is downloading).