Fatal error: Uncaught Error: Class 'Nextend\SmartSlider3\Widget\AbstractWidget' not found in C:\xampp\htdocs\wp-content\plugins\smart-slider-3\Nextend\SmartSlider3\Widget\Thumbnail\Basic\ThumbnailBasic.php:18 Stack trace: #0 {main} thrown in C:\xampp\htdocs\wp-content\plugins\smart-slider-3\Nextend\SmartSlider3\Widget\Thumbnail\Basic\ThumbnailBasic.php on line 18