While attempting to add to a small save with one train and no stations:

Error while running event cybersyn::on_configuration_changed
__cybersyn__/scripts/migrations.lua:331:attempt to index field 'manager' (a nil value)
stack traceback:
__cybersyn__/scripts/migrations.lua:331: in function 'on_config_changed'
__cybersyn__/scripts/main.lua:952: in function <__cybersyn__/scripts/main.lua:951>

Edit: If I enable the GUI setting, the error no longer occurs.

Same error. On newish save with no trains or tracks yet. disabled mod. added to nope list.

Same error. On loading newish save that was created with mod enabled, with no trains or tracks yet. disabled mod. added to nope list.

This should be fixed in the latest version.

Confirmed, the issue seems to be resolved in 1.2.15. Thank you for the quick fix!