details.php throws exception that isRootRival is not defined

[mmorella-dev]

[21-Dec-2022 19:29:48 Europe/Berlin] PHP Fatal error:  Uncaught mysqli_sql_exception: Incorrect integer value: '' for column `vadaproject_db`.`flagsdb`.`isRootRival` at row 1 in /Applications/XAMPP/xamppfiles/htdocs/directory/insert.php:330
Stack trace:
#0 /Applications/XAMPP/xamppfiles/htdocs/directory/insert.php(330): mysqli_query(Object(mysqli), 'INSERT INTO fla...')
#1 {main}
  thrown in /Applications/XAMPP/xamppfiles/htdocs/directory/insert.php on line 330