Null tilde expansions?

[Greg Badros <gjb@cs.washington.edu>]

Is there any way to make ~notauser not cause an error (similar to the
null globbing option)?

I'd like this to give me the home directories of all the users in group oo_gang

users=(`ypcat group  | awk -F: '/^oo_gang\>/ { printf $4 }' | tr , ' '`)
dirs=~$^users

without first having to eliminate users from $users which no longer
exist (our sysadmins aren't good about eliminating users from groups
when the remove the user account).

Thanks,
Greg