Fetching field values only if they exist and applying them automatically as entity labels
As far as I remember, field_get_items() returns an array of items. 
In your case something like:

    if (count($address)) {
       print $address[0]['value'];

       if (count($entrance)) {
          print ' ' . $entrance[0]['value'];
       }

      if (count($apartment_number)) {
         print ' ' . $apartment_number[0]['value'];
      }
   }


should work.