Ticket #54558: 54558.1.diff

src/wp-includes/block-editor.php

@@ -468 +468 @@
          */
         $backup_global_post = ! empty( $post ) ? clone $post : $post;
 
+        foreach ( $preload_paths as &$path ) {
+                if ( is_string( $path ) && ! str_starts_with( $path, '/' ) ) {
+                        $path = '/' . $path;
+                }
+
+                if ( is_array( $path ) ) {
+                        foreach( $path as &$part ) {
+                                if ( is_string( $part )
+                                        && $path === strtolower( $part )
+                                        && ! str_starts_with( $part ) ) {
+                                        $part = '/' . $part;
+                                }
+                        }
+                }
+        }
+
         $preload_data = array_reduce(
                 $preload_paths,
                 'rest_preload_api_request',