Ecshop Vietnam Application Error

The application could not run because of the following error:

Type: E_NOTICE [8]

Message: Undefined variable: display in /home/glkozeq7b8/public_html/modules/category.php

Line: 59

Stack trace:

#0 /home/glkozeq7b8/public_html/modules/category.php(59): ErrorHandler->handleError(8, 'Undefined varia...', '/home/glkozeq7b...', 59, Array)
#1 /home/glkozeq7b8/public_html/index.php(40): include_once('/home/glkozeq7b...')
#2 {main}