V13: Incorrectly parsing item id by DeliveryApiContentIndex caused incorrect information when deleting a content item

[elit0451]

Details

Fixes #15792

• As a result of the new V13: Delivery API composite id handler #15305, we didn't parse a noncomposite id correctly, so we returned an empty string instead of null, resulting in Lucene error (seen in the logs):
  
• • Which on its hand caused incorrect data in DeliveryApiContentIndex when a content item has been deleted.
• This PR fixes that and makes sure we follow the practice: int.ToString(CultureInfo.InvariantCulture) when converting ints to strings.

Test

• Follow the Steps to reproduce in the original issue
  • Make sure that the total amount of items and the number of items in the items collection is correct after deleting a content item (both variant and invariant) and making a GET request to
    /umbraco/delivery/api/v2/content

[kjac]

Good stuff ❤️

[biapar]

Hi. Which Umbraco version contain this fix?

[kjac]

Hi @biapar ... this is in 13.3 😄