Ticket #18975: 18975.5.diff

src/wp-admin/widgets.php

@@ -182 +182 @@
 
         if ( isset($_GET['addnew']) ) {
                 // Default to the first sidebar
-                $sidebar = array_shift( $keys = array_keys($wp_registered_sidebars) );
+                $keys = array_keys( $wp_registered_sidebars );
+                $sidebar = array_shift( $keys );
 
                 if ( isset($_GET['base']) && isset($_GET['num']) ) { // multi-widget
                         // Copy minimal info from an existing instance of this widget to a new instance