xSiteable Autoloader : /home/xsiteable/xsiteable.org/lib/classes/tidy.php not found. [tidy]

Fatal error: Uncaught Error: Class 'tidy' not found in /home/xsiteable/xsiteable.org/xs/extensions/modules/generic_content.module.php:43 Stack trace: #0 [internal function]: xs_module_generic_content->___modules(NULL) #1 /home/xsiteable/xsiteable.org/xs/Events/EventStack.class.php(684): call_user_func(Array, NULL) #2 /home/xsiteable/xsiteable.org/xs/Events/EventStack.class.php(617): xs\Events\EventStack->run_action('XS_MODULES', false) #3 /home/xsiteable/xsiteable.org/index.php(48): xs\Events\EventStack->action() #4 {main} thrown in /home/xsiteable/xsiteable.org/xs/extensions/modules/generic_content.module.php on line 43