Use type checking instead of null coalescing

Author: warcooft

system/HTTP/RedirectResponse.php

@@ -93,8 +93,8 @@ public function withInput()
     {
         $session = service('session');
         $session->setFlashdata('_ci_old_input', [
-            'get'  => $_GET,
-            'post' => $_POST,
+            'get'  => is_array($_GET) ? $_GET : [],
+            'post' => is_array($_POST) ? $_POST : [],
         ]);
 
         $this->withErrors();