PHP8.4 Deprecation fix

[davisriska]

Fixes PHP 8.4 deprecation warnings/errors

I first tried array|null and ?array but they were added in PHP8.0 and PHP7.1 respectively. So I reviewed what happens with the null and it just gets ignored with the if. I think this fix should work with 5.4.

Shapefile\Geometry\MultiPolygon::__construct(): Implicitly marking parameter $polygons as nullable is deprecated, the explicit nullable type must be used instead
Shapefile\Geometry\GeometryCollection::__construct(): Implicitly marking parameter $geometries as nullable is deprecated, the explicit nullable type must be used instead
Shapefile\Geometry\MultiPolygon::__construct(): Implicitly marking parameter $polygons as nullable is deprecated, the explicit nullable type must be used instead

[Malezha]

@gasparesganga please consider this pull request as soon as possible, as this is a very critical issue.