Just downloaded the mod and keep getting the following error with crash at start up.

The scenario level caused a non-recoverable error.
Please report this error to the scenario author.

Error while running event level::on_chunk_generated (ID 12)
...ng/Factorio/temp/currently-playing/frontier-extended.lua:422: attempt to perform arithmetic on field 'x' (a nil value)
stack traceback:
...ng/Factorio/temp/currently-playing/frontier-extended.lua:422: in function 'handler'
core/lualib/event_handler.lua:47: in function <core/lualib/event_handler.lua:45>

I get this on the first action after pressing <tab> if that action is not one of wasd. If I take a step first, this crash does not happen. I'm guessing there is a field that is initialized only once the player moves.

This is fixed in 1.2.5. Thanks for the report.