Widgets: Revert format of `sidebars_widgets`.

Restores the data format of the `sidebars_widgets` theme mod to its pre [41555]
format. It can trigger PHP warnings after switching themes if that mod has not
been removed previously.

Fixes #39693.


Built from https://develop.svn.wordpress.org/trunk@41673


git-svn-id: http://core.svn.wordpress.org/trunk@41507 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/theme.php

@@ -690,7 +690,7 @@ function switch_theme( $stylesheet ) {
 	}
 
 	if ( is_array( $_sidebars_widgets ) ) {
-		set_theme_mod( 'sidebars_widgets', $_sidebars_widgets );
+		set_theme_mod( 'sidebars_widgets', array( 'time' => time(), 'data' => $_sidebars_widgets ) );
 	}
 
 	$nav_menu_locations = get_theme_mod( 'nav_menu_locations' );

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.9-alpha-41672';
+$wp_version = '4.9-alpha-41673';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.

wp-includes/widgets.php

@@ -1286,6 +1286,7 @@ function wp_map_sidebars_widgets( $existing_sidebars_widgets ) {
 
 	// Sidebars_widgets settings from when this theme was previously active.
 	$old_sidebars_widgets = get_theme_mod( 'sidebars_widgets' );
+	$old_sidebars_widgets = $old_sidebars_widgets['data'];
 
 	if ( is_array( $old_sidebars_widgets ) ) {