Fix curl_copy_handle_basic_008.phpt when display_errors is On

(Thanks Chris Jones)

ext/curl/tests/responder/get.php

@@ -1,5 +1,6 @@
 <?php
-  switch($_GET['test']) {
+  $test = isset($_GET['test']) ? $_GET['test'] : null;
+  switch($test) {
     case 'post':
       var_dump($_POST);
       break;