Uninitialized string offset helpers/css-parser.php on line 110

Hello Geoffrey,

hope you had a good start into the new Year.
To prevent this Warning, you can add a query.

if( array_key_exists($idx,$code) ){
    $c = $code[$idx];
}

This query will check, if the offset exists and will only then acces the array offset.
Be aware, this could also be intentional by the developer to clear $c with null if the offset is missing.
I am writing this from my laptop and could not check the hole sourcecode.

Have a nice day.