No warning feedback when trying to set empty password in the users & groups tool

Binary package hint: gnome-system-tools

This bug was found on Ubuntu Natty 64 bits.

Steps to reproduce:
1) In a terminal, type "users-admin" to open to Users & Groups management tool.
2) Click on the "Modify" button next to the password field.
3) Enter your correct current password.
4) For the new password and the confirm password entries, leave the fields empty.
5) Click on the Validate button. Notice no warning or feedback whatsoever is given.
6) Redo the steps 2, this time using the new supposedly empty password as the current password
7) Type whatever you want (but the same twice) in the new password and confirm password fields.
8) Press the Validate button. An error will occur, saying the authentication failed (meaning the current password is not empty as it should!)

What should have happened instead:
When we first tried to modify the current password to empty, the tool should have warned us that we couldn't do this for safety reasons (or should have really changed the user's password to empty).

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: gnome-system-tools 2.32.0-0ubuntu7
ProcVersionSignature: Ubuntu 2.6.38-8.42-generic 2.6.38.2
Uname: Linux 2.6.38-8-generic x86_64
Architecture: amd64
Date: Sun May 22 21:30:36 2011
EcryptfsInUse: Yes
ExecutablePath: /usr/bin/users-admin
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110427.1)
ProcEnviron:
 SHELL=/bin/bash
 PATH=(custom, user)
 LANGUAGE=fr_CA:en
 LANG=fr_CA.UTF-8
SourcePackage: gnome-system-tools
UpgradeStatus: No upgrade log present (probably fresh install)