Fix behavior when a session is not found

[maxbes]

Apache::Session modules are supposed to die when they cannot find a session, instead of returning undef (a46b17a58ff57415d450184d6e665ea14862daba)

Thankfully, a typo in the code means they still die, with the following message:

Session cannot be tied: Can't modify non-lvalue subroutine call of &AutoLoader::AUTOLOAD at /usr/local/share/perl/5.26.1/Apache/Session/Store/MongoDB.pm line 72

Attempting to fix the typo breaks LemonLDAP::NG::Common::Session :

my $var = {
    'storageModuleOptions' => {
        'db_name' => 'sessions',
        'collection' => 'psessions',
    },
    'kind' => 'Persistent',
    'storageModule' => 'Apache::Session::MongoDB',
    'id' => '5efe8af397fc3577e05b483aca964f1c',
    'force' => 1,
    'info' => {
        '_loginHistory' => {
            'successLogin' => [
                {
                    '_utime' => 1616505142,
                    'ipAddr' => '127.0.0.1'
                }
            ]
        },
        '_updateTime' => '20210323131222',
        '_session_uid' => 'dwho'
    }
};

my $ps = Lemonldap::NG::Common::Session->new($var);
use Data::Dumper;
print Dumper($ps);

(no session is created)