Logout error

I got this err when I echo do_shortcode(‘[logout]’) and I press logout button with [login-logout-toggle], and user do not logout at all. :

Warning
: Cannot modify header information - headers already sent by (output started at C:\xampp\htdocs\yellowpage\wp-content\plugins\front-end-only-users\Functions\Output_Buffering.php:9) in
C:\xampp\htdocs\yellowpage\wp-content\plugins\front-end-only-users\Shortcodes\Insert_Logout.php
on line
47

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