Update for when post sync arguments don't include the full meta.

[BrendanJercich]

This may be at the root of recent indexing issues on a certain client site. For whatever reason, the $post_args array no longer seems to contain the meta fields from ACF, where it's kind of assumed that lat/long will be stored. It's not clear to me whether this is ideal for precedence, ie whether those post fields are getting updated by a post-save action for the purposes of get_field before or after this hook fires. But latitude and longitude don't change that much for map locations, so presumably even if there is a precedence issue, the indexing will pick up the change the next time a sync is called?