In "on_built_entity", you overwrite the "entity"-key from the event with the "created_entity"-key. A "script_raised_built"-event has no "created_entity"-key, just an "entity"-key. This fixes it:

if event.entity == nil then
    event.entity = event.created_entity
end

Sorry it took me so long. I was busy with a bunch of things.
Should be fixed now, along with a while bunch of new features.

The mod Neo Hazard Lights (0.0.2) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event neo-hazard-lights::on_configuration_changed
LuaEntity API call when LuaEntity was invalid.
stack traceback:
[C]: in function 'index'
__neo-hazard-lights/control.lua:229: in function 'verify_lamps_data'
neo-hazard-lights/control.lua:618: in function <neo-hazard-lights/control.lua:618>

In future, please open a new thread if it's a different issue.