Can't use get_current_screen() in Simple custom post order plugin.

Hi,
I want this plugin only works when admin is in sticky post list. (/wp-admin/edit.php?show_sticky=1)

To get current admin page, I used get_current_screen() inside the SCPO_Engine, in simple-custom-post-order.php.
And then the whole site gone blank.

Anyone knows why?

https://wordpress.org/plugins/simple-custom-post-order/