Ever since i installed leaf child theme I am getting a warning message

whenever I try to update a post or whatnot the message I am getting is:

Warning: Cannot modify header information – headers already sent by (output started at /home2/bradz/public_html/wp-content/themes/leaf-child-master/functions.php:34) in /home2/bradz/public_html/wp-includes/pluggable.php on line 875

how do i fix this in the leaf child theme? I installed the child theme from the developers website and at first it was fine but now I am having a problem. I have not added any code in the editor FYI. Thanks for your help!