Nested transition clobbers parent update

[halfnelson]

https://v3.svelte.technology/repl?version=3.0.0-beta.20&gist=6d537f9c99a5f089b6dd415412173c39

What is supposed to happen:
When clicking on delete, the delete button should animate out, then the item should be removed from the list

What happens:
When you click on delete, the button animates out, but the item stays.

Investigation:
Upon a deeper investigation using debugger, it seems that it is due to two nested calls to group_outros. The first call sets up the removal of the item from the list to happen after all outros are complete. The second call is due to the if statement in the delete button component, this replaces the content of the outros variable and thus the outro_complete callback to remove the item from the list is never fired.

[Panya]

It was fixed in 3.5.3