Comment 31 for bug 160862

The fix (as linked aboved) is simply to ensure split() stops when it has 4 items. That way, we ensure we won't pass more arguments than the D-Bus binding expects, which prevents the script from dying. So the garbage gets packed in the last field, i.e. users that are members of the group. This is not a problem since clients will simply get unknown users with strange names and ignore them.

Ideally, we should check that every field is valid, but for a backport, a one-line fix that works is better. Anyway, if the line is not correct, we can hardly behave better than clearing the list of members of the group.