PHP error on Drupal 6

Hi,

I get this error in drush when I run cron:

WD php: preg_match(): Delimiter must not be alphanumeric or backslash in                                                                                         
/www/xxxx/site/sites/all/modules/themekey/themekey_base.inc on line 379.[error]

I don't know if it's related at my settings difficulties explained here :
https://drupal.stackexchange.com/questions/262043/themekey-use-wilcard

Thanks