A PHP Error was encountered

Severity: Notice

Message: Trying to access array offset on value of type null

Filename: controllers/School.php

Line Number: 836

Backtrace:

File: /home/uniform/html/unimap2/ci/application/controllers/School.php
Line: 836
Function: _error_handler

File: /home/uniform/html/unimap2/index.php
Line: 315
Function: require_once