Potential security issue in is_super_admin

[Stachethemes]

function is_super_admin( $user_id = false ) {

	if ( ! $user_id ) {
		$user = wp_get_current_user();
	} else {
		$user = get_userdata( $user_id );
	}

        ...
}

If user is logged in as super admin and do is_super_admin(0); it will return true;

It would be best to use strict comparison:

function is_super_admin( $user_id = false ) {

	if ( false === $user_id ) {
		$user = wp_get_current_user();
	} else {
		$user = get_userdata( $user_id );
	}

        ...
}

Adding strict comparison for checking the user_id

Trac ticket: https://core.trac.wordpress.org/ticket/58860