The mod ChunkyChunks - Configurable Geodesic Grid (1.4.2) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event ChunkyChunks::on_tick (ID 0)
Invalid surface name or index.
stack traceback:
ChunkyChunks/control.lua:61: in function 'chunky'
ChunkyChunks/control.lua:249: in function <ChunkyChunks/control.lua:195>
stack traceback:
[C]: in function 'draw_line'
ChunkyChunks/control.lua:61: in function 'chunky'
ChunkyChunks/control.lua:249: in function <ChunkyChunks/control.lua:195>

This crash occurred when I wasn't doing anything. Maybe my radar was going or something, I don't know.

Version: 1.4.3
Date: 2020-08-17 19:34
Bugfixes:
- Fixed missing check for deleted surfaces, thanks HanBai for the report
https://mods.factorio.com/mod/ChunkyChunks/discussion/5f3abb45b7a232fc87dcb54e
Features:
- Shortcut and hotkey toggles are back. But they are not optimised yet, so don't spam them
too much ;> They kind of slipped in since they were kind of implemented and I had to fix the bug.

Funny that this would be happening many hours after deleting the surfaces, but I guess that’s bugs. Thanks for the fix!

When chunks are generated ChunkyChunks stores a list ofwhich "superchunks" that are 10 000 tiles wide and high squares have chunks in them. And these also contain a reference to the surface. The chunks themselves are not stored, only these handful of superchunks which are empty structures. But they are used when redrawing the grids, which happens if you change your ChunkyChunks settings. So something probably did happen that triggered refreshing the grids for some player with an old reference.