fixed edge case for AMv3 POA geni_update_users
There was a weird edge case for AMv2 PerformOperationalAction geni_update_users.
Somehow, an undef was used as $key, which was passed along from call to call all the way from GeniAM::PerformOperationalAction to GeniCM::AddKeys's $keychecker sub. In that sub, the code $key ne "" caused a crash.
This should now be fixed, by adding if (defined($key)) to GeniAM.pm.in