An uncaught Exception was encountered

Type: Error

Message: Call to a member function row_array() on boolean

Filename: /var/www/html/application/models/sitecontrol/Testresults_model.php

Line Number: 820

Backtrace:

File: /var/www/html/application/controllers/sitecontrol/Testresults.php
Line: 258
Function: next_prev

File: /var/www/html/index.php
Line: 315
Function: require_once