From <https://bugzilla.novell.com/show_bug.cgi?id=819524>: nscd crashes while processing a netgroup entry where one or more values from the (host,user,domain) triple are absent. Reproducable by adding this line to /etc/netgroup: powerusers (,miquels,) (,torvalds,) (,fubar,) and running getent netgroup powerusers.
Fixed by 50fd745