A PHP Error was encountered

Severity: Notice

Message: Undefined index: HTTP_USER_AGENT

Filename: libraries/Mylibrary.php

Line Number: 147

Backtrace:

File: /var/www/html/application/libraries/Mylibrary.php
Line: 147
Function: _error_handler

File: /var/www/html/application/controllers/News.php
Line: 18
Function: __construct

File: /var/www/html/index.php
Line: 294
Function: require_once