Users: Adjust [45708] to make sure `wp_update_user()` does not issue a `WP_Error` if a single site was previously set up as Multisite and there's still a `spam` field in the user table.

Add a unit test.

Props azaozz, SergeyBiryukov.
Fixes #45747.
Built from https://develop.svn.wordpress.org/trunk@45874


git-svn-id: http://core.svn.wordpress.org/trunk@45685 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/user.php

@@ -1665,7 +1665,7 @@ function wp_insert_user( $userdata ) {
 
 	$user_activation_key = empty( $userdata['user_activation_key'] ) ? '' : $userdata['user_activation_key'];
 
-	if ( isset( $userdata['spam'] ) && ! is_multisite() ) {
+	if ( ! empty( $userdata['spam'] ) && ! is_multisite() ) {
 		return new WP_Error( 'no_spam', __( 'Sorry, marking a user as spam is only supported on Multisite.' ) );
 	}
 

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.3-alpha-45873';
+$wp_version = '5.3-alpha-45874';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.