Magento 1 script to reset attribute models if model can not be instantiated (because module is uninstalled)

magento_clean_attribute_source_models.php

<?php
require_once 'app/Mage.php';
Mage::app();
$autoFix = true;

class Clean_Attribute_Source_Models
{
    private $autofix;

    private $modelFields = ['backend_model', 'frontend_model', 'source_model'];

    /**
     * @var Mage_Core_Model_Resource
     */
    private $resource;

    public function __construct($autofix = false)
    {
        $this->autofix = $autofix;
        $this->resource = Mage::getSingleton('core/resource');
    }

    public function run()
    {
        foreach ($this->getAttributeRows() as $attributeRow) {
            $this->handleAttributeRow($attributeRow);
        }
    }

    private function handleAttributeRow($attributeRow)
    {
        foreach ($this->modelFields as $modelField) {
            if (!empty($attributeRow[$modelField]) && !$this->instantiateModel($attributeRow[$modelField])) {
                echo "$modelField '" . $attributeRow[$modelField] . "' [".$attributeRow['attribute_id']."] could not be resolved\n";
                $this->fixAttributeRowModelField($attributeRow['attribute_id'], $modelField);
            }
        }
    }

    private function fixAttributeRowModelField($attributeId, $modelField)
    {
        $eavAttributeTableName = $this->resource->getTableName('eav_attribute');
        $query = 'UPDATE '.$eavAttributeTableName.' SET `'.$modelField.'`="" WHERE `attribute_id`='.$attributeId;
        $this->getWriteConnection()->query($query);
    }

    private function instantiateModel($modelName)
    {
        try {
            $model = Mage::getModel($modelName);
        } catch (Exception $e) {
            return false;
        }

        if (empty($model)) {
            return false;
        }

        return true;
    }

    private function getAttributeRows()
    {
        $eavAttributeTableName = $this->resource->getTableName('eav_attribute');
        $query = 'SELECT attribute_id,' . implode(',', $this->modelFields) . ' FROM ' . $eavAttributeTableName;
        return $this->getReadConnection()->fetchAll($query);
    }

    private function getReadConnection()
    {
        return $this->resource->getConnection('core_write');
    }

    private function getWriteConnection()
    {
        return $this->resource->getConnection('core_write');
    }
}

(new Clean_Attribute_Source_Models($autoFix))->run();