Fatal error: Uncaught TypeError: call_user_func_array(): Argument #1 ($callback) must be a valid callback, class "RevSliderWidget" not found in /home/reveal22/public_html/wp-includes/class-wp-hook.php:341 Stack trace: #0 /home/reveal22/public_html/wp-includes/class-wp-hook.php(365): WP_Hook->apply_filters(NULL, Array) #1 /home/reveal22/public_html/wp-includes/plugin.php(522): WP_Hook->do_action(Array) #2 /home/reveal22/public_html/wp-includes/widgets.php(1884): do_action('widgets_init') #3 /home/reveal22/public_html/wp-includes/class-wp-hook.php(341): wp_widgets_init('') #4 /home/reveal22/public_html/wp-includes/class-wp-hook.php(365): WP_Hook->apply_filters(NULL, Array) #5 /home/reveal22/public_html/wp-includes/plugin.php(522): WP_Hook->do_action(Array) #6 /home/reveal22/public_html/wp-settings.php(742): do_action('init') #7 /home/reveal22/public_html/wp-config.php(99): require_once('/home/reveal22/...') #8 /home/reveal22/public_html/wp-load.php(50): require_once('/home/reveal22/...') #9 /home/reveal22/public_html/wp-blog-header.php(13): require_once('/home/reveal22/...') #10 /home/reveal22/public_html/index.php(17): require('/home/reveal22/...') #11 {main} thrown in /home/reveal22/public_html/wp-includes/class-wp-hook.php on line 341