Fatal error: Uncaught Exception: /var/www/html/extensions/DownloadButton/extension.json is not a valid JSON file. in /var/www/html/includes/registration/ExtensionRegistry.php:374 Stack trace: #0 /var/www/html/includes/registration/ExtensionRegistry.php(255): ExtensionRegistry->readFromQueue() #1 /var/www/html/includes/Setup.php(252): ExtensionRegistry->loadFromQueue() #2 /var/www/html/includes/WebStart.php(93): require_once('...') #3 /var/www/html/index.php(44): require('...') #4 {main} thrown in /var/www/html/includes/registration/ExtensionRegistry.php on line 374