Has this already been fixed?
This sounds like your configuration file became broken, because HCL loads the language file set in the config.php file on that line.
You should check the config.php file for the absence of this line:
$conf['lang'] = 'english';
If this line isn't anywhere in the file, you should add it somewhere between the <?php and ?>.
You should make sure there isn't a comment mark (//) in front of the line.