Fix missing link variable in test

Author: nielsdos

ext/mysqli/tests/gh11438.phpt

@@ -77,6 +77,10 @@ print "done!";
 --CLEAN--
 <?php
 require_once 'connect.inc';
+if (!$link = my_mysqli_connect($host, $user, $passwd, $db, $port, $socket)) {
+    printf("[clean] Cannot connect to the server using host=%s, user=%s, passwd=***, dbname=%s, port=%s, socket=%s\n",
+        $host, $user, $db, $port, $socket);
+}
 $link->query('DROP USER shatest');
 $link->query('DROP USER shatest@localhost');
 ?>