Widgets: Fix an “Invalid value” warning when adding a new widget in the Customizer.

This fixes a regression introduced in [50996] where sites that have been opted-out of the block-based widget editor experienced an “Invalid value.” error when adding a new widget to a sidebar in the Customizer.

This was caused by the early return value was changed to `null` from `$value` when set to an empty `array`, resulting in the widget being evaluated as invalid elsewhere.

Props jamesros161, caseymilne, naoki0h, ixkaito, zieladam, noisysocks, hellofromTonya.
Fixes #53479.
Built from https://develop.svn.wordpress.org/trunk@51232


git-svn-id: http://core.svn.wordpress.org/trunk@50841 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/class-wp-customize-widgets.php

@@ -1413,7 +1413,7 @@ final class WP_Customize_Widgets {
 		global $wp_widget_factory;
 
 		if ( array() === $value ) {
-			return;
+			return $value;
 		}
 
 		if ( isset( $value['raw_instance'] ) && $id_base && wp_use_widgets_block_editor() ) {

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.8-beta3-51231';
+$wp_version = '5.8-beta3-51232';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.