Ticket #33602: 33602.diff

wp-includes/widget-functions.php

@@ -739 +739 @@
  * @return bool true if the sidebar is in use, false otherwise.
  */
 function is_active_sidebar( $index ) {
-        $index = ( is_int($index) ) ? "sidebar-$index" : sanitize_title($index);
-        $sidebars_widgets = wp_get_sidebars_widgets();
-        $is_active_sidebar = ! empty( $sidebars_widgets[$index] );
+        $index             = ( is_int( $index ) ) ? "sidebar-$index" : sanitize_title( $index );
+        $sidebars_widgets  = wp_get_sidebars_widgets();
+        $is_active_sidebar = ! empty( $sidebars_widgets[ $index ] );
 
         /**
+         * Addresses case where a widget instance is still in sidebars_widgets but
+         * is not actually registered.
+         *
+         * @ticket 33602
+         */
+        if ( true === $is_active_sidebar ) {
+
+                global $wp_registered_widgets;
+                $widget_area_contents = $sidebars_widgets[ $index ];
+                $active_widget_count  = count( $widget_area_contents );
+
+                foreach ( $widget_area_contents as $widget_instance ) {
+
+                        if ( ! array_key_exists( $widget_instance, $wp_registered_widgets ) ) {
+                                $active_widget_count--;
+                        }
+                }
+                $is_active_sidebar = ( 0 < $active_widget_count );
+        }
+
+        /**
          * Filter whether a dynamic sidebar is considered "active".
          *
          * @since 3.9.0