how to hide the orange sticky header in this page

I get the following PHP notice when trying to create a child theme. I doubt it’s anything serious, but figured I’d let the developer know.

Notice:  Trying to get property 'ID' of non-object in /home/customer/www/xxx.com/public_html/wp-includes/class-wp-query.php on line 4044

Notice:  Trying to get property 'post_title' of non-object in /home/customer/www/xxx.com/public_html/wp-includes/class-wp-query.php on line 4046

Notice:  Trying to get property 'post_name' of non-object in /home/customer/www/xxx.com/public_html/wp-includes/class-wp-query.php on line 4048

in site identity section there is Logo Maximum Width (px) block is not working i have set the value to 200px but at website front nothing happens !