Make Address/Billing profile optional

Some Drupal Commerce setups may not have "billing profile" attached to an order.

It's an uncommon situation, but there is a patch that makes it possible.

When someone tries to complete his Order without Billing profile attached to it, he gets an error:
Error: Call to a member function get() on null в Drupal\commerce_google_analytics\EventSubscriber\SendOrderAnalyticsSubscriber->buildGaPushParams() line 56.

There's no real reason to assume that Billing profile is present and to mandatory collect some fields:

       'city' => $profileAddress->getLocality(),
        'region' => $profileAddress->getAdministrativeArea(),
        'country' => $profileAddress->getCountryCode(),

They are optional and we should add it if they're present.