Please, somebody, help me out.. How do I fix this?

I kept on receiving this each time I tried to register an account and create a subsite on the frontend of my WordPress multisite

Warning: call_user_func_array() expects parameter 1 to be a valid callback, array must have exactly two members in /var/www/u0851948/public_html/**/wp-includes/class-wp-hook.php on line 289

Below is what i have on line 289;

$value = call_user_func_array( $the_['function'], array_slice( $args, 0, (int) $the_['accepted_args'] ) );

Thank you!