Plugin Login-Logout crashes WordPress

Plugin Login-Logout crashes WordPress 3.1.3 when you install it.
It is very small plugin. It shows one widget with “login-logout” link instead of WordPress default widget.
It uses such code to register widget:

function login_logout_widget_init() {
	register_widget('WP_Widget_Login_Logout');
	do_action('widgets_init');
}
add_action('init', 'login_logout_widget_init', 1);

Full code of the plugin.

Maybe somebody could help or advise what is wrong in the code of the plugin?