Eu estava usando o CodeIgniter 3.0.0 com PHP 5.6.

Ontem atualizei para o PHP 7 e comecei a receber o seguinte erro: -

Uncaught TypeError: Argument 1 passed to CI_Exceptions::show_exception() must be
 an instance of Exception, instance of Error given, called in /my/file/path/app/system/core/Common.php on line 658 and defined in /my/file/path/hgx_portal/app/system/core/Exceptions.php:190
Stack trace:
#0 /my/file/path/hgx_portal/app/system/core/Common.php(658): CI_Exceptions->show_exception(Object
(Error))
#1 [internal function]: _exception_handler(Object(Error))
#2 {main}
  thrown in /my/file/path/hgx_portal/app/system/core/Exceptions.phpon line 190