I got this error. I blueprinted something with this mod in it, and tried to remove everything of it again (wrong place).
I made a buleprint, then changed the placement of the signposts and "selected new content" for the blueprint. then if you place the blueprint and hover over it with an deconstruction planner, there are "+" marks and when you try to remove it the mod (and so gamesave) crashes.
The mod Attach Notes (0.4.8) caused a non-recoverable error.
Please report this error to the mod author.
Error while running event attach-notes::on_player_deconstructed_area (ID 69) attach-notes/scripts/entity-notes/controller.lua:203: attempt to index field '?' (a nil value)
stack traceback: attach-notes/scripts/entity-notes/controller.lua:203: in function 'func' attach-notes/framework.lua:98: in function <attach-notes/framework.lua:97>
EDIT: forgot to mention I'm playing Factorio 1.0.0.