https://imgur.com/KPEkWae

The game crashes upon placing the buy chest. This is with a new Freeplay game with Krastorio2 Overhaul.

I just released a patch to fix this, go ahead and test it out!

You're awesome, djmango! Thank you so much!

Still having the same issue with the new patch.

Same, with Space Exploration pack

Deadlocks Stacking (from the deadlock's Stacking Belt boxes and loaders), research gates your mods ability to scan the base resources for copper, Iron, coal and stone, and with Coal being indexed as null it throws the error when placing the buy chest. I have triple checked the source of this error, and can confidently trace it back to NOT having done this research. Once the deadlocks stacking level 1 research is completed, click the black market button and run the scan, Voila, Solved.
I have now triple confirmed this with two other fresh starts, So longs as you have deadlocks stacking level 1 researched, and black market researched, it will work without errors. Deadlocks Stacking Level 1 research is the source of your issue.

I have the same error.
I do not have any Deadlocks Stacking mods.

My modlist:
https://i.imgur.com/ckGON8s.png

This is fixed in the latest patch

Well then, it seems to me that you could gate Black Market Buyers behind the first tier of Deadlock Stacking if Deadlock Stacking is present.

Bump. Still having this issue, not having Deadlock Stacking installed
Same thing with Coal Nil,
Seems like theres another mod doing this?
it happens when i click on "New order"

"
The mod Black Market 2 (2.0.5) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event BlackMarket2::on_gui_click (ID 1)
BlackMarket2/control.lua:2681: attempt to index field 'coal' (a nil value)
stack traceback:
BlackMarket2/control.lua:2681: in function <BlackMarket2/control.lua:2398>
"

Maybe put the coin there instead of coal.