51423: wp_privacy_generate_personal_data_export_file fixes type match for array_merge (PHP 8)

src/wp-admin/includes/privacy-tools.php

@@ -357,9 +357,6 @@ function wp_privacy_generate_personal_data_export_file( $request_id ) {
  $email_address
 	);
 
-	// And now, all the Groups.
-	$groups = get_post_meta( $request_id, '_export_data_grouped', true );
-
 	// First, build an "About" group on the fly for this report.
 	$about_group = array(
  /* translators: Header for the About section in a personal data export. */
@@ -388,10 +385,24 @@ function wp_privacy_generate_personal_data_export_file( $request_id ) {
  ),
 	);
 
-	// Merge in the special about group.
-	$groups = array_merge( array( 'about' => $about_group ), $groups );
+	// And now, all the Groups.
+	$groups = get_post_meta( $request_id, '_export_data_grouped', true );
+	if ( is_array( $groups ) ) {
+ $groups = array_merge( array( 'about' => $about_group ), $groups );
+ $groups_count = count( $groups );
+	} else {
+ if ( false !== $groups ) {
+ _doing_it_wrong(
+ __FUNCTION__,
+ /* translators: %s: post meta key. */
+ sprintf( __( 'The %s post meta must be an array.' ), "<code>'_export_data_grouped'</code>" ),
+ '5.8.0'
+ );
+ }
 
-	$groups_count = count( $groups );
+ $groups = null;
+ $groups_count = 0;
+	}
 
 	// Convert the groups to JSON format.
 	$groups_json = wp_json_encode( $groups );