WP-Optimize - Fatal Error When Activating WPML with Multi-Domain Setup and WP-Optimize Active

Overview of the issue

If you are using WP-Optimize – Clean, Compress, Cache plugin alongside WPML and A different domain per language feature is enabled, it leads to the following fatal error:

Fatal error: Uncaught Error: Call to a member function get_current_language() on null in /wpml-url-cached-converter.php on line 18.

Workaround

Please, make sure of having a full site backup of your site before proceeding.

• Open …/wp-content/plugins/wp-optimize/cache/class-wpo-cache-config.php file.
• Look for line 225.
• Comment out that line:

  			//'uploads'									=> wp_normalize_path(wp_upload_dir()['basedir']),