Ticket #31675: register-sidebar-id.31675.1.diff

src/wp-includes/widgets.php

@@ -803 +803 @@
 
         $i = count($wp_registered_sidebars) + 1;
 
+        // Ensure we have a valid ID.
+        if ( empty( $args['id'] ) ) {
+                _doing_it_wrong( __METHOD__, __( 'The id argument should not be empty.' ), '4.2.0' );
+        }
+
         $defaults = array(
                 'name' => sprintf(__('Sidebar %d'), $i ),
                 'id' => "sidebar-$i",