REST API: Send a 500 status code when JSON encoding fails.

Previously, a 200 status code would be sent despite the 500 status code present in the response body.

Props hermpheus, lalitjalandhar.
Fixes #53056.


git-svn-id: https://develop.svn.wordpress.org/trunk@51960 602fd350-edb4-49c9-b593-d223f7449a82

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

@@ -497,6 +497,7 @@ class WP_REST_Server {
 			$json_error_message = $this->get_json_last_error();
 
 			if ( $json_error_message ) {
+				$this->set_status( 500 );
 				$json_error_obj = new WP_Error(
 					'rest_encode_error',
 					$json_error_message,