Media: Check the `posts_per_page` value in `wp_ajax_query_attachments()` before using it as a divisor.

This avoids a "Division by zero" PHP warning if a plugin changes the `posts_per_page` value to zero.

Follow-up to [51145].

Props 2linctools, kapilpaul, audrasjb.
Fixes #53773.
Built from https://develop.svn.wordpress.org/trunk@51485


git-svn-id: http://core.svn.wordpress.org/trunk@51096 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/ajax-actions.php

@@ -3003,7 +3003,9 @@ function wp_ajax_query_attachments() {
 		$total_posts = $count_query->found_posts;
 	}
 
-	$max_pages = ceil( $total_posts / (int) $attachments_query->query['posts_per_page'] );
+	$posts_per_page = (int) $attachments_query->query['posts_per_page'];
+
+	$max_pages = $posts_per_page ? ceil( $total_posts / $posts_per_page ) : 0;
 
 	header( 'X-WP-Total: ' . (int) $total_posts );
 	header( 'X-WP-TotalPages: ' . (int) $max_pages );

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.9-alpha-51484';
+$wp_version = '5.9-alpha-51485';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.