Media: Sanity check array value in `wp_prepare_attachment_for_js()`.

This adds a sanity check to the return value of the `image_downsize` filter
in `wp_prepare_attachment_for_js()` to avoid undefined offest notices.

Props justinbusa for initial patch.
Fixes 34437.
Built from https://develop.svn.wordpress.org/trunk@39107


git-svn-id: http://core.svn.wordpress.org/trunk@39049 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/media.php

@@ -3159,8 +3159,10 @@ function wp_prepare_attachment_for_js( $attachment ) {
 
 			/** This filter is documented in wp-includes/media.php */
 			if ( $downsize = apply_filters( 'image_downsize', false, $attachment->ID, $size ) ) {
-				if ( ! $downsize[3] )
+				if ( empty( $downsize[3] ) ) {
 					continue;
+				}
+
 				$sizes[ $size ] = array(
 					'height'      => $downsize[2],
 					'width'       => $downsize[1],

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.7-beta1-39106';
+$wp_version = '4.7-beta1-39107';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.