Warning: Use of undefined constant DEMO - assumed 'DEMO' (this will throw an Error in a future version of PHP)
Otherwise the debug mode cannot be used in the Contao back end (if warnings are not otherwise ignored). This also makes the code more compatible towards PHP 8.0.
This PR fixes the following PHP warning:
Otherwise the debug mode cannot be used in the Contao back end (if warnings are not otherwise ignored). This also makes the code more compatible towards PHP 8.0.