REST API: Correct variable type in `WP_Rest_Server::serve_batch_reque…

…st_v1()`.

`wp_parse_str()` expects an array as the second parameter.

Follow-up to [49252].

Props antonvlasenko.
See #61593.

git-svn-id: https://develop.svn.wordpress.org/trunk@58688 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/rest-api/class-wp-rest-server.php

@@ -1667,7 +1667,7 @@ public function serve_batch_request_v1( WP_REST_Request $batch_request ) {
 			$single_request = new WP_REST_Request( isset( $args['method'] ) ? $args['method'] : 'POST', $parsed_url['path'] );
 
 			if ( ! empty( $parsed_url['query'] ) ) {
-				$query_args = null; // Satisfy linter.
+				$query_args = array();
 				wp_parse_str( $parsed_url['query'], $query_args );
 				$single_request->set_query_params( $query_args );
 			}