How can we fix the bug if we have 1.7.7.0 and we don't want to update?
EDIT: You can fix this by replacing this file in your 1.7.7.0: EditCmsPageHandler.php
With the same file from 1.7.7.1: src\Adapter\CMS\Page\CommandHandler\EditCmsPageHandler.php
Here is the file from 1.7.7.1: EditCmsPageHandler.php