Undefined index error

I receive the following error after I edit a user, author, etc…

Notice: Undefined index: crb_user_blocked in /home/lapresse/public_html/test/wp-content/plugins/wp-cerber/cerber-users.php on line 55

Warning: Cannot modify header information – headers already sent by (output started at /home/lapresse/public_html/test/wp-content/plugins/wp-cerber/cerber-users.php:55) in /home/lapresse/public_html/test/wp-includes/pluggable.php on line 1223

Error does not appear when WP cerber plugin is disabled

Thanks for your help !

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