ACF resolve_post_object_source filter returns incorrect result when empty/null

[jacobarriola]

Describe the bug
If using an ACF Post Object field in a repeater, there are instances where a user may save an empty entry. As is, the current filter assumes all values are non-nullable and thus fetches for a post with no ID. As a result, the first product returns.

To Reproduce
Steps to reproduce the behavior:

1. Create an ACF repeater field
2. Create one Post Object sub field
3. On a page, add 2 repeater items, but only selecting a product for 1 of the fields, leaving the 2nd blank
4. Save page
5. Run a GraphQL query for the items

Expected behavior
The query should return an array with two objects: one product + one null

Actual behavior
The query returns an array with two product objects

Screenshots

Desktop (please complete the following information):

• WooGraphQL: 0.7
• WooCommerce: 4.7.1
• ACF: 5.8.6

[kidunot89]

This should not longer be and issue with the new WPGraphQL ACF extension