Index: src/wp-includes/media.php
===================================================================
--- src/wp-includes/media.php	(revision 57666)
+++ src/wp-includes/media.php	(working copy)
@@ -5065,9 +5065,6 @@
 				$srcs = array();
 
 				$shortcode_attrs = shortcode_parse_atts( $shortcode[3] );
-				if ( ! is_array( $shortcode_attrs ) ) {
-					$shortcode_attrs = array();
-				}
 
 				// Specify the post ID of the gallery we're viewing if the shortcode doesn't reference another post already.
 				if ( ! isset( $shortcode_attrs['id'] ) ) {