Fixed PHP 8.1 incompatibility on upgrade from older versions Fixed ignore immage alt attribute error

\app\code\Nwdthemes\Revslider\changelog.txt \app\code\Nwdthemes\Revslider\composer.json \app\code\Nwdthemes\Revslider\Controller\Adminhtml\Revslider.php \app\code\Nwdthemes\Revslider\Helper\Framework.php \app\code\Nwdthemes\Revslider\Model\Revslider\RevSliderNavigation.php \app\code\Nwdthemes\Revslider\Model\Revslider\RevSliderObjectLibrary.php \app\code\Nwdthemes\Revslider\Model\Revslider\RevSliderOutput.php \app\code\Nwdthemes\Revslider\Model\Revslider\RevSliderSlide.php \app\code\Nwdthemes\Revslider\Model\Revslider\RevSliderSlider.php \app\code\Nwdthemes\Revslider\Model\Revslider\Admin\RevSliderAdmin.php \app\code\Nwdthemes\Revslider\Model\Revslider\Admin\Includes\RevSliderFunctionsAdmin.php \app\code\Nwdthemes\Revslider\Model\Revslider\Admin\Includes\RevSliderTracking.php \app\code\Nwdthemes\Revslider\Model\Revslider\ExternalSources\RevSliderFacebook.php \app\code\Nwdthemes\Revslider\Model\Revslider\Front\RevSliderFront.php \app\code\Nwdthemes\Revslider\Setup\UpgradeData.php \app\code\Nwdthemes\Revslider\view\adminhtml\templates\release_log.phtml \app\code\Nwdthemes\Revslider\view\adminhtml\web\admin\assets\js\admin.min.js \app\code\Nwdthemes\Revslider\view\adminhtml\web\admin\assets\js\editor.min.js \app\code\Nwdthemes\Revslider\view\adminhtml\web\admin\assets\js\modules\admin.js \app\code\Nwdthemes\Revslider\view\adminhtml\web\admin\assets\js\modules\slide.js \app\code\Nwdthemes\Revslider\view\base\web\public\assets\css\rs6.min.css \app\code\Nwdthemes\Revslider\view\base\web\public\assets\js\rbtools.min.js