phpMyFAQ Fatal error

Uncaught exception: 'TypeError'

Message: 'phpMyFAQ\Strings::htmlentities(): Argument #1 ($string) must be of type string, null given, called in /app/add.php on line 70'

Stack trace:

#0 /app/add.php(70): phpMyFAQ\Strings::htmlentities(NULL)
#1 /app/index.php(793): require('/app/add.php')
#2 {main}

Thrown in '/app/src/phpMyFAQ/Strings.php' on line 274