Docs: Correct documentation for _wp_preview_meta_filter().

The `$single` parameter is passed via the `get_post_metadata` filter and has no default value.

Includes minor code layout fixes for consistency with the formatting of other long conditionals in core.

Follow-up to [56714].

Props rodrigosprimo.
Fixes #61645.

git-svn-id: https://develop.svn.wordpress.org/trunk@58717 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/revision.php

@@ -1107,24 +1107,24 @@ function _wp_upgrade_revisions_of_post( $post, $revisions ) {
  * @param mixed  $value     Meta value to filter.
  * @param int    $object_id Object ID.
  * @param string $meta_key  Meta key to filter a value for.
- * @param bool   $single    Whether to return a single value. Default false.
+ * @param bool   $single    Whether to return a single value.
  * @return mixed Original meta value if the meta key isn't revisioned, the object doesn't exist,
  *               the post type is a revision or the post ID doesn't match the object ID.
  *               Otherwise, the revisioned meta value is returned for the preview.
  */
 function _wp_preview_meta_filter( $value, $object_id, $meta_key, $single ) {
-
 	$post = get_post();
-	if (
-		empty( $post ) ||
-		$post->ID !== $object_id ||
-		! in_array( $meta_key, wp_post_revision_meta_keys( $post->post_type ), true ) ||
-		'revision' === $post->post_type
+
+	if ( empty( $post )
+		|| $post->ID !== $object_id
+		|| ! in_array( $meta_key, wp_post_revision_meta_keys( $post->post_type ), true )
+		|| 'revision' === $post->post_type
 	) {
 		return $value;
 	}
 
 	$preview = wp_get_post_autosave( $post->ID );
+
 	if ( false === $preview ) {
 		return $value;
 	}