newsupernova/vendor/magento/module-theme/etc/adminhtml/di.xml

<?xml version="1.0"?>
<!--
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
-->
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <type name="Magento\Theme\Block\Adminhtml\Wysiwyg\Files\Content">
        <arguments>
            <argument name="storageHelper" xsi:type="object">Magento\Theme\Helper\Storage\Proxy</argument>
        </arguments>
    </type>
    <type name="Magento\Theme\Block\Adminhtml\Wysiwyg\Files\Tree">
        <arguments>
            <argument name="storageHelper" xsi:type="object">Magento\Theme\Helper\Storage\Proxy</argument>
        </arguments>
    </type>
    <type name="Magento\Theme\Block\Adminhtml\Wysiwyg\Files\Content\Uploader">
        <arguments>
            <argument name="storageHelper" xsi:type="object">Magento\Theme\Helper\Storage\Proxy</argument>
        </arguments>
    </type>
    <type name="Magento\Backend\App\AbstractAction">
        <plugin name="themeRegistrationFromFilesystem" type="Magento\Theme\Model\Theme\Plugin\Registration"/>
    </type>
    <type name="Magento\Framework\View\Element\Message\MessageConfigurationsPool">
        <arguments>
            <argument name="configurationsMap" xsi:type="array">
                <item name="default_message_identifier" xsi:type="array">
                    <item name="renderer" xsi:type="const">\Magento\Framework\View\Element\Message\Renderer\EscapeRenderer::CODE</item>
                </item>
            </argument>
        </arguments>
    </type>
    <type name="Magento\Theme\Model\Design\Config\Validator">
        <arguments>
            <argument name="fields" xsi:type="array">
                <item name="header" xsi:type="string">email_header_template</item>
                <item name="footer" xsi:type="string">email_footer_template</item>
            </argument>
        </arguments>
    </type>
</config>