Allow null awareness values to remove a client from a room

Author: alecgeatches

src/wp-includes/collaboration/class-wp-http-polling-sync-server.php

@@ -122,7 +122,7 @@ public function register_routes(): void {
 			),
 			'awareness' => array(
 				'required' => true,
-				'type'     => 'object',
+				'type'     => array( 'object', 'null' ),
 			),
 			'client_id' => array(
 				'minimum'  => 1,