Simplify the check for false-y `child_of` arg.

Props SergeyBiryukov.
See #25230, [25245].


Built from https://develop.svn.wordpress.org/trunk@25270


git-svn-id: http://core.svn.wordpress.org/trunk@25236 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/post.php

@@ -3665,7 +3665,7 @@ function get_pages( $args = '' ) {
 	if ( !in_array( $post_type, $hierarchical_post_types ) )
 		return $pages;
 
-	if ( $parent > 0 && empty( $child_of ) && ! isset( $args['child_of'] ) )
+	if ( $parent && ! $child_of )
 		$hierarchical = false;
 
 	// Make sure we have a valid post status