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