How do I make it so that the all users page is not a white screen?

The answer is “Undo what you did”, but you did not explain what you did so I am assuming that what you did was change the “Screen Option” value on the wp-admin/users.php page. If that is the case, you need to get into the database via PhpMyAdmin or some other tool and change the users_per_page value for your user.

You can also add the following to your theme’s functions.php, load a page, and then remove it.

// change '1' to your user ID
// 20 is the default value so it should set things back to normal
update_user_meta(1,'users_per_page',20);