Error on Activation

Warning: call_user_func_array() expects parameter 1 to be a valid callback, class ‘Sunny_Activator’ not found in /home/d563029/public_html/wp-includes/plugin.php on line 505

The plugin generated 290 characters of unexpected output during activation. If you notice “headers already sent” messages, problems with syndication feeds or other issues, try deactivating or removing this plugin.

https://ww.wp.xz.cn/plugins/sunny/