Undoing spawn deletion creates an undeletable spawn #87
I'm changing the object of this ticket. I realize that the fact that materialized spawns being re-spawned when the start date of a scheduled txn is changed is a problem, but fixing this requires an important re-design and is outside the scope of this release. The real problem here is the fact that it's not possible to delete those spawns.
For a while, I couldn't reproduce the bug, but now I got it: It's undone spawn deletion that are buggy. If you delete a spawn and then undo the deletion, the spawn that came back will be un-deletable. With a few undo chains, it's also possible to end up with a lot of "duplicate spawns", which, if undone/redone enough, will all be un-deletable.