Question

When I upgraded Magento, the AheadWorks module was disabled.

When saving on admin, System -> Configuration -> Advanced -> then click Save Config

An error occurred while saving this configuration: Notice: Trying to
get property of non-object in
MAGENTO_ROOT/app/code/core/Mage/Adminhtml/Model/Config/Data.php
on line 135

I’ve been searching in many times to find the solution but i got nothing.

http://www.magentocommerce.com/bug-tracking/issue/?issue=13819

How to fix that?

Answer 1

Find the following lines of code around line 135 of app/code/core/Mage/Adminhtml/Model/Config/Data.php:

$backendClass = $fieldConfig->backend_model;
if (!$backendClass) {
    $backendClass = 'core/config_data';
}

and replace it by:

if (isset($fieldConfig->backend_model)) {
    $backendClass = $fieldConfig->backend_model;
}
if (!isset($backendClass)) {
    $backendClass = 'core/config_data';
}

Hope this helps.