Perl: Fix JSONization of ArrayObjects

Created by: AnaTofuZ

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@wing328 @yue9944882

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Sorry, I had created a bug in the https://github.com/OpenAPITools/openapi-generator/pull/12891 PR. It fails when trying to convert an array of Objects to JSON.

my $object = WWW::OpenAPIClient::Object::Pet->new->from_hash(
  {
    tags => [ WWW::OpenAPIClient::Object::Tag->new->from_hash({id => 123, name => 'test' }), WWW::OpenAPIClient::Object::Tag->new->from_hash({ id => 321, name => 'foo'}) ],
  });

my $json = JSON->new->convert_blessed->encode($object);
say $json;

got json

"{\"tags\":[\"\",\"\"],\"photoUrls\":[]}"

The JSON I want is this.

"{\"tags\":[{\"id\":123,\"name\":\"test\"},{\"id\":321,\"name\":\"foo\"}],\"photoUrls\":[]}"

The cause was that I forgot to return a value in primitive type that did not match any if statement. I fixed it and added a test