Meta Boxes: Use a unique name for the nonce of the meta box loader.

Fixes a case where saving in the block editor fails if there are two `_wpnonce` arguments in the request, one overriding the other so that `use_block_editor_for_post()` wasn't able to check the nonce properly.

Props Chouby.
See #45253.
Built from https://develop.svn.wordpress.org/trunk@44938


git-svn-id: http://core.svn.wordpress.org/trunk@44769 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/edit-form-blocks.php

@@ -120,7 +120,7 @@ $meta_box_url = add_query_arg(
 		'post'                  => $post->ID,
 		'action'                => 'edit',
 		'meta-box-loader'       => true,
-		'_wpnonce'        => wp_create_nonce( 'meta-box-loader' ),
+		'meta-box-loader-nonce' => wp_create_nonce( 'meta-box-loader' ),
 	),
 	$meta_box_url
 );

wp-admin/includes/post.php

@@ -2071,7 +2071,7 @@ function use_block_editor_for_post( $post ) {
 
 	// We're in the meta box loader, so don't use the block editor.
 	if ( isset( $_GET['meta-box-loader'] ) ) {
-		check_admin_referer( 'meta-box-loader' );
+		check_admin_referer( 'meta-box-loader', 'meta-box-loader-nonce' );
 		return false;
 	}
 

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.2-alpha-44937';
+$wp_version = '5.2-alpha-44938';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.