Index: wp-includes/media.php
===================================================================
--- wp-includes/media.php	(revision 22832)
+++ wp-includes/media.php	(working copy)
@@ -1752,7 +1752,7 @@
 						'full'      => __('Full Size'),
 					) );
 
-					foreach ( $sizes as $value => $name ) : ?>
+					foreach ( (array) $sizes as $value => $name ) : ?>
 						<#
 						var size = data.sizes['<?php echo esc_js( $value ); ?>'];
 						if ( size ) { #>