Added missing "cron_interval" default value

config/defaults.config.php

@@ -72,6 +72,10 @@ return [
 		// Deny public access to the local user directory.
 		'block_local_dir' => false,
 
+		// cron_interval (Integer)
+		// Minimal period in minutes between two calls of the "Cron" worker job.
+		'cron_interval' => 5,
+
 		// cache_driver (database|memcache|memcached|redis)
 		// Whether to use Memcache or Memcached or Redis to store temporary cache.
 		'cache_driver' => 'database',