The Samba-Bugzilla – Bug 10065
The "null passwords" option is deprecated
Last modified: 2013-08-01 20:17:47 UTC
The smb.conf man page fails to mention that this option is deprecated even though the "testparm" tool reports this warning.
If the option is not deprecated then testparm should be fixed.
If it is then the smb.conf man page should mention that.
I believe this also carries over into Samba 4.