PHP error with get_string() breaks plugin functionality

This is referenced in a bunch of different posts about images being broken or caches not reloading, but none of them show the error. Please link other posts to this one for discussion.

Error:

Call to a member function get_string() on array in /usr/local/apache2/htdocs/wp-content/plugins/w3-total-cache/Util_Environment.php on line 1042

Offending code is here:

        static public function is_w3tc_pro( $config = null ) {
                $result = $config->get_string( 'plugin.type' ) == 'pro' ||
                        $config->get_string( 'plugin.type' ) == 'pro_dev' ||
                        Util_Environment::is_w3tc_enterprise( $config ) ||
                        ( defined( 'W3TC_PRO' ) && W3TC_PRO );

                return $result;
        }

It appears that $config is not an object but an array.

Workaround suggested here is to simply return false if you’re not using W3TC Pro:

	static public function is_w3tc_pro( $config = null ) {
		return false;
	}