Returns a table of train ids for the specified section.
Returns nil if the section id is not provided..
Returns false if the section id is invalid.
Returns an empty table if the section id is valid but empty of trains.
Splitting at index=1 results in multiple empty trains being created.
Can be prevented by an atc_speed > 0 check by the user, but easier just to return false and do nothing.
Maverick2797
orwell96