Script error on OpenTTD 1.7.1

This script doesn't work on OpenTTD 1.7.1 included in Ubuntu Linux 18.04 64 bits. It gives the following error on the console:

Your script made an error: the index doesn't exist

CALLSTACK *FUNCTION [main()] migrations-1/info.nut line [23]

LOCALS [this] TABLE dbg: [misc] [squirrel] Failed to compile 'migrations-1/info.nut'

And it doesn't show up on NewGRF settings archive list.