Check that `languages_codes` is defined before iterating over it.
Check that `languages_codes` is defined before iterating over it.

Fixes #921

openfoodfacts/openfoodfacts-server,openfoodfacts/openfoodfacts-server,openfoodfacts/openfoodfacts-server,openfoodfacts/openfoodfacts-server,openfoodfacts/openfoodfacts-server