Add guard to anonymous function

[afragen]

Fixes #412

Somehow release->artifacts->package is null and sending to pick_artifact_by_lang() returns a type error. Adding a guard to the anonymous function should mitigate this issue.

[github-actions]

🧪 Test this PR on Playground

[costdev]

This change is fine as-is, though I'd also be curious whether the value being stored in the transient should be checked. If, for example, a release document should always have artifacts->package, if that's missing from a release document, we may consider skipping it, or possibly erroring, if needed.

[afragen]

If the transient didn't return an array wouldn't the error be different?

[costdev]

If the transient didn't return an array wouldn't the error be different?

It would, though I wasn't referring to the CACHE_RELEASE_PACKAGES array itself, I was referring to each release document inside it. If a release document doesn't have ->artifacts->package, should it even be stored in the cache array?

The cache is set here:

fair-plugin/inc/packages/namespace.php

Line 874 in 8f3ab3c

set_site_transient( CACHE_RELEASE_PACKAGES, $releases );

So if get_latest_release_from_did() returns a release document without artifacts->package, is there any reason to add this invalid WP "package" to the cache?

Moreover:

1. I don't quite understand how this situation occurred. How was a DID detected, but the package didn't have any package artifacts?
2. In cases such as malformed metadata, I don't think the code should be getting this far. I think it may make sense to return a WP_Error object from get_latest_release_from_did() if a release doesn't have a package artifact, then add is_wp_error() checks in all the appropriate places. Testing required of course.

[afragen]

Is this a product of the transient being an empty array?

[costdev]

Nope, look at line 726 in the file touched by this PR - so the transient isn't an empty array. It's due to hitting a missing package artifact when looking at each release document inside that array.

[afragen]

That's essentially what the guard protects.