error when creating new site in multisite

when i create a new site via network admin im getting this error message

Warning: Creating default object from empty value in /home4/ardge25/public_html/wp-includes/ms-functions.php on line 1502

Warning: Cannot modify header information - headers already sent by (output started at /home4/ardge25/public_html/wp-includes/ms-functions.php:1502) in /home4/ardge25/public_html/wp-includes/pluggable.php on line 896

can anyone advise what i should do or have a solution for me?

thanks