activity_pub: fix case when featured collection misses orderedItems field

A temporary clutch to fix the fetching actors from Friendica, of course pins are not federating with them yet.

Ideally, we should check if collection has items or orderedItems property. For example, current Mastodon does this.

This was also reported to Friendica: https://github.com/friendica/friendica/issues/10427#issuecomment-1107934351