Error Exception in seeding the DB

[Fulcinator]

Good Morning everyone, I'm installing Timegrid in a Ubuntu 18.04 environment with php 7.2.

When installing timegrid, after installing all the dependencies and completing the migration of tables, when seeding,

php artisan db:seed

one of the php script fails: in particular in CountriesSeeders.php at the line:

public function run() {
[....]
$countries = Countries::getList();
[...]

the error is a generic Error Exception, reporting the following message:

[ErrorException]
sizeof(): Parameter must be an array or an object that implements Countable

I tried to figure out how the Countries class was built but with no result, also this error seems to be related to php version >=7.2 which produces a warning that artisan transforms to an error.

Does anyone know a possible solution? Thanks for helping