Error after Magento upgrade from 1.7.0.2 to 1.9.0.1

getFallbackScheme() Magento Error

Fatal error: Call to a member function getFallbackScheme() on a non-object in /app/code/core/Mage/Core/ Model/Design/Package.php on line 447

/**
* Use this one to get existing file name with fallback to default
*
* $params['_type'] is required
*
* @param string $file
* @param array $params
* @return string
*/
public function getFilename($file, array $params)
{
Varien_Profiler::start(__METHOD__);
$this->updateParamDefaults($params);
$result = $this->_fallback(
$file,
$params,
$this->_fallback->getFallbackScheme(
$params['_area'],
$params['_package'],
$params['_theme']
)
);
Varien_Profiler::stop(__METHOD__);
return $result;
}

Solution – clear cache

Delete the files in the /var/cache folder.