Magento: Temporary fix for failed configuration saves. See http://screencast.com/t/7yGn07BMGSY

gistfile1.php

<?php

// app/code/core/Mage/Adminhtml/Model/Config/Data.php: 135:

/**
 * Get field backend model
 */
$backendClass = $fieldConfig->backend_model;
if (!$backendClass) {
    $backendClass = 'core/config_data';
}

// Just silence the notice while you save.

/**
 * Get field backend model
 */
$backendClass = @$fieldConfig->backend_model; // Note the '@' here.
if (!$backendClass) {
    $backendClass = 'core/config_data';
}

// Or, a more permanent fix, if you're into
// fixing core bugs.

/**
 * Get field backend model
 */
if (!is_object($fieldConfig) || empty($fieldConfig->backend_model)) {
    $backendClass = 'core/config_data';
}
else {
    $backendClass = $fieldConfig->backend_model;
}