add null check to optional values
add null check to optional values

sphereio/commercetools-php-sdk,sphereio/sphere-php-sdk,sphereio/sphere-php-sdk,sphereio/commercetools-php-sdk,sphereio/sphere-php-sdk,sphereio/commercetools-php-sdk,sphereio/sphere-php-sdk,sphereio/commercetools-php-sdk